Weather Forecasts

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Administrative guidelines for forecasting snowfall amounts

The following paragraphs explain forecasting snow events, amounts, ranges, and terminology. The following guidelines should be used when issuing snowfall or mixed precipitation events. This guidance only refers to forecasting expected snowfall or mixed precipitation events. This is in addition to forecasting sky condition, temperature, wind, fog, haze, precipitation chances, or any other meteorological parameter or can be used exclusively for snow accumulation forecasts in a specific region of a large synoptic area, a mesoscale forecast, or a local forecast.

Snowfall Accumulation Terms and Definitions:

Snowfall Accumulation/Accumulation – Depth of snowfall.
Snowfall Range/Range – The spread or width in inches of snowfall accumulations.
Snowfall Accumulation Forecast – Expected snowfall accumulations normally expressed as a specific range.
Narrative Contingent Accumulation Forecast/Contingent Forecast – A snowfall accumulation forecast that is based on contingent possibilities or probabilities, usually expressed part of the forecast as a range dependent on variables.
Synoptic – Large scale weather features covering multiple regions, generally 500-1500 miles or larger.
Regional – Areas within a synoptic area usually covering multiple states normally several hundred to 500 miles.
Local – Forecast within a local area, normally not larger than 100 miles in diameter.
Mesoscale – Areas of current meteorological activity such as fronts, squall lines, thunderstorms, etc. usually within a local or regional forecast area.
Microscale – A small area of meteorological interest usually 1 mile of less in scope.
Mixing – A combination of frozen, freezing, and liquid precipitation that hinders snowfall accumulation. Examples are snow, snow pellets, ice pellets, sleet, freezing rain, and rain.
Isolated/Isolated up to/Isolated to – Terms used to describe the amount of snowfall over the forecasted range that is possible in isolated areas, generally areas in less than 10% of the forecast area.
Locally/Locally up to – Terms used to describe the amount of snowfall that is possible over or under (in cases of mixing) the forecasted range in certain areas within a forecast, generally areas in 10-25% of the forecast area.
Non-symmetric, and/or skewed accumulations – Snowfall amounts vary significantly with a forecast area due to geographical and/or dynamic meteorological anomalies, or other circumstances causing a wide variation in snowfall accumulation amounts.
Uncertainty – Explanation of meteorological conditions that are present which could significantly affect the forecasted snowfall range.
Narrative – Explanation of meteorological conditions present that explains the forecast.
Forecast Parentheses – Explanation of uncertainty in a forecast area.
Range Intersection/Overlap – Terms used to verify if the actual median snowfall amount fell within the forecasted range.
Range Boundaries – Upper and lower limits of a forecasted snowfall range.
Verification Accumulation Mean/Verification Mean – The mean snowfall in a forecast area, excluding extremes and anomalies.
Verification Accumulation Range/Verification Range – The average snowfall range in a forecast area, excluding extremes and anomalies.

The snowfall accumulation forecast is normally defined by accumulation ranges, contingent ranges and other or additional accumulation information. In order to determine an appropriate range, an analysis of at least two and preferably three global numerical weather models should be used to determine accumulation estimates or a mean accumulation amount and then the snowfall accumulation forecast should be fine tuned with mesoscale or regional models before a final update. If time permits, an analysis of current and future atmospheric conditions in a specific forecast area should be performed to determine the extent of any mitigating circumstances affecting snowfall accumulation. These can be as simple as determining a surface temperature to as complex as identifying and specifying branching dendrite formation in a dendritic growth zone (DGZ).

A snowfall accumulation range will normally be determined 48 hours or more in advance and a final update will be issued 2-6 hours before any forecast region has had significant impacts. If time permits, an interim forecast may be issued about 24-36 hours before significant accumulations are expected to begin. The snowfall forecast and narrative contingent forecast accumulation ranges should be issued according to the guidelines provided below.

Use of a narrative contingent accumulation forecast (specified or unspecified/non-specified) for higher or lower localized or contingent amount ranges should normally be included in the narrative of a local forecast or in the parenthesis of a synoptic, regional/mesoscale snowfall accumulation forecast. Local forecasts may identify ranges and amounts above or below the forecast range along with the uncertainty associated with the forecast all within the forecast text. No uncertainty parentheses are required and generally should not be used on local forecasts unless they are a forecast synopsis and/or part of a group of snowfall accumulation forecasts. Synoptic, regional, or other large mesoscale area snowfall accumulation forecasts should clearly explain any uncertainty in the forecast and, at a minimum, nonspecifically indicate expected fluctuations in accumulation amounts in the parentheses following the text forecast and, if necessary, should include a specific contingent accumulation  range.

“Isolated”/“isolated up to”/“isolated to”/”locally”/”locally up to” amounts may be used, if necessary, if they can’t be included in the normal forecast range or they better describe the situation. Isolated generally indicates occurrences in less than 10% (<10%) of the forecast area while local ranges or “locally up to” or “locally” indicates occurrences in greater than 10% but less than 25% of the forecast area. They are added as an informational tool to further explain and understand potential accumulations in a forecast area.

Localized amounts may be delineated as a range (higher or lower than the forecasted range) or a specific “up to” amount (only in instances above the forecasted range) and “isolated” may be  delineated as a range or an amount with a “+” symbol. Normally, “Isolated….”, “locally”, and “locally up to” should only be used to specify areas where amounts are HIGHER than the forecasted regional or local area ranges but “locally” may be used to forecast lower amounts due to mixing within the forecast area. Also, localized ranges should normally touch the upper (all snow or mixed) or lower boundary (mixed only) of the forecast range.

Synoptic, regional, or other large mesoscale area snowfall accumulation forecasts should clearly explain any uncertainty in the forecast in the parentheses following the text forecast.

Outside the forecast range, use of a specific localized amounts range and/or a non-specific and “isolated up to” or similar verbiage amounts is encouraged when uncertainty exists and the ranges or amounts are reasonable, possible, probable, and anticipated to occur in some places of the forecast area. Do not use the specified localized amount range or “isolated up to” amounts if they are determined to be unlikely or unexpected. Normally use the terms “Isolated” or “isolated up to” or “locally up to” or locally” to define accumulations above the expected range. Use “locally” or other specific phrases to convey contingent accumulation ranges due to mixing/change to rain that lower than the forecasted accumulations amounts.  Use of the “isolated” or “locally” verbiage without the use of a locality range may be used if the forecast range is determined to be sufficient and certain places could get over the forecast range amount. “Isolated” or “locally up top” verbiage indicates those places will be less than 10% of the forecast area and “locally”, when used as a higher amount, indicates those areas will be between 10% and 25% of the forecast area.

Specific localized amounts for all snow events should only be used to define the upper boundaries of the range forecasted. Specific localized amount ranges may be used to define ranges below or above the forecasted range. Unspecified localized amounts should only be used during mixed precipitation events when the possibility or probability of the occurrence is uncertain and cannot be reasonably and specifically determined. In those instances, follow the general guidance for mixed precipitation. Localized amounts and ranges or “isolated” verbiage should be included in the verbiage of the snowfall forecast.

Nonspecific verbiage indicating higher or lower amounts should generally explained after the forecast by enclosing in parentheses. Verbiage similar to the following should be used to explain mixing: mixing, some mixing, mixing likely, mixing/sleet, mixing/rain, mostly rain, mixing probable, mixing possible, significant mixing, etc. Use the verbiage that best explains the situation in the forecast area.

Also, identify areas within the forecast area, either in the forecast text or the uncertainty parentheses, that may suggest more or less snowfall amounts based on uncertainties and contributions to the overall accumulation such as mixing, rain, advection, mesoscale banding/deformation, convection, instability, frontogenesis/frontolysis, thermal and moisture gradients, surface temperature and other atmospheric anomalies, proximity to bodies of water (hyrodsopheric influences), frozen bodies of water (cryospheric influences), mountain effects (orographic influences), surface/boundary layer influences or other factors. A simple explanation of these effects is advised. The effects of mixing on accumulation may be mentioned and explained either in the local forecast snowfall text or in the uncertainty parentheses following a local or other larger area forecast.

Forecasting Snowfall Amount Guidelines:

For all snow events or mixed precipitation events generally use the following guidelines for snowfall accumulation ranges and other snowfall accumulation information. This is general guidance and should apply in most instances but occasionally events or forecast areas, especially larger area or storms with significant mixing, will require a deviation from these guidelines.

If the mean expected snowfall accumulation is expected to be…

* Less than 5“ – use no more than a 3 inch range (2 inch maximum range is preferable) with no localized specified heavier ranges or isolated references (i.e. preferred T-1”, T-2”, 1-2”, 2-3”, 3-4”, 1-3”, 2-4”, 3-5”)
Note: T-3”, 1-4”, 2-5” should only be used in cases of higher uncertainty, especially mixing, marginal temperatures or other local variables.

* 5-8” – use a range of 2-5” (4” maximum range is preferable, 5” maximum in certain instances for >= 7”). Specify localized higher amounts above the forecast range, if necessary, in a 2” range, and do not use isolated higher amounts verbiage. Do not use a 5” range for a mean accumulation of less than 7”. (i.e. preferred 4-6”, 5-7”, 6-8”, 8-10”, 3-7”, 4-8”, 6-10”, 5-10”)
Note: Except for 5-10”, use even numbers for ranges if possible and warranted.

* 9-12” – use a range of 4-6”. Specify localized higher amounts above the forecast range, if necessary, in a 2” range with a 5-6” forecasted range or specify a 2-4” localized higher amounts range with a 4” forecasted range. If necessary, specify isolated higher amounts “isolated up to” or similar verbiage but normally not more than 2” above the specified localized higher range or, if possible, include any isolated amounts within the specified localized range and omit the isolated amounts. (i.e. preferred 6-10”. 8-12”, 10-15”, 6-12”, 8-14”, 10-16)
Note: Use isolated and local verbiage as necessary, explicitly, and only if needed.

* 13-16”- use a range of 5-8” (10” maximum in certain instances for >= 15”). Specify localized higher amounts above the forecast range, if necessary, in a 4-6” range. If necessary, specify isolated higher amounts “isolated up to” or similar verbiage but normally not more than 4” above the specified localized higher range or in some cases use the + to indicate extremes. If possible, include any isolated amounts within the specified localized range and omit the isolated amounts. (i.e. preferred 8-14”, 10-15”, 10-16”, 12-18”, 14-20”, 15-20”, 8-16”, 10-18”, 12-20”. Use 8-18” or 10-20” only where uncertainty is high or forecast region is large with much variability expected)
Note: Use isolated and local verbiage as necessary, explicitly, and only if needed.

*16-20”- use a range of 6-12” (least amount is best, if possible) Specify localized higher amounts above the forecast range, if necessary, in a 4-6” range. If necessary, specify isolated higher amounts “isolated up to” or similar verbiage but normally not more than 4” above the specified localized higher range or in some case use the + to indicate extremes. If possible, include any isolated amounts within the specified localized range and omit the isolated amounts. (i.e. preferred 12-18”, 14-20”, 16-22”, 18-24”, 12-20”, 14-22”, 16-24”, and only if necessary 10-20”, 15-25”, 12-24”)

*Over 20”- use a range of 6-12” (least amount is best, if possible) Specify localized higher amounts above the forecast range, if necessary, in a 4-6” range. If necessary, specify isolated higher amounts “isolated up to” or similar verbiage but normally not more than 6” above the specified localized higher range or in some cases use the + to indicate extremes. If possible, include any isolated amounts within the specified localized range and omit the isolated amounts. (i.e. preferred 18-24”, 20-26”, 24-30”,  15-25”,  16-24”, 18-26”, 20-28”, 22-30”, 15-25”, 18-28”, 20-30”, and only if necessary 14-26”, 16-28”, 18- 30”.

If the mean expected snowfall accumulation includes significant mixing the ranges may be expanded somewhat but generally not more than 25%.

Remember … The least possible range of forecasted and specified localized higher amounts is preferred but not at the expense of omitting any conditional possibilities or probabilities. Use of “isolated up to” amounts or “+” amounts should only be used if deemed necessary and generally not at all if the expected mean amount is 8” or less. Above an expected mean of >= 6” events generally try to use even number ranges or 5” increments beginning with 5”, 15” and so on.” If median snowfall is expected to be more than 10”, the mean amount expected does not have to be in the center of the forecast range if more localities of the expected snowfall/mixed precipitation are expected to fall in the higher or lower part of the range (i.e. median is expected 12“ with all snow and you expect some mixing then a range of 8-14” indicates you expect more accumulations to fall in the lower part of the range than the upper part of the range, possibly due to mixing). Ideally, this would be better than adding contingent locality ranges and may allow you to omit or reduce the localized amounts range or require the need for other additional explanatory verbiage, especially in medium range snowfall/mixing events or low significant mixing events.

Verification Standards:

Note: When determining the percentage that forecast and verification ranges intersect always use forecasted range spread as the basis for the amount that ranges intersect (overlap). This will ensure that ranges are restricted and no larger than the expected snowfall amount range guidelines.

J :) Accurate/Excellent Forecast:

For local forecasts, the forecasted accumulation range was essentially correct or slightly high or low at the peripheral of the forecasted accumulation ranges (forecasted accumulation range falls completely within or mostly within the verification accumulation range, i.e. ranges overlap significantly) and/or the verification mean falls in or near the center of the forecasted accumulation range or in large forecast geographical regions with large disparities the verification accumulation mean was within the forecasted accumulation range and/or the forecasted accumulation range significantly intersects (ranges overlap significantly, > 40%) the verification accumulation range, not including local extremes or anomalies.

OR

A narrative contingency forecast (local or regional) recognized, mentioned, and included as a forecasted possibility or probability, a specific accumulation range and geographical area(s), either above or below the actual forecasted accumulation range, that was verified by an accumulation mean within the contingent forecasted accumulation range not including local extremes or anomalies, or a contingent forecasted accumulation range that is within or significantly intersects (ranges overlap significantly, > 40%) the verification accumulation range, not including local extremes or anomalies.

OR

The forecast narrative (local or regional) explicitly indicated areas of the forecast geographical area expected to get much higher or much lower amounts that would require expanded forecast accumulation ranges outside the normal guidelines that reasonably and understandably invalidated the mean accumulation amount or range intersection criteria but is consistent, understandable, and reasonable, though not completely representative relative to the forecasted accumulation range and/or the contingent forecasted accumulation range and is slightly to moderately outside the upper and/or lower boundaries of the contingent forecasted accumulation range. Guidelines are used to restrict forecast accumulation ranges, contingent accumulation ranges, or local/isolated ranges based on the expected accumulation  over the forecast area, otherwise, all encompassing wide ranges could be used making all accumulation forecasts of little value (i.e. An expected snowfall of 10” is expected; if no guidelines and limits are placed on the main, contingent and isolated/locally range accumulations, the forecast could read T-20”, isolated 20”+, possible 0-10” with mixing, which tells use basically nothing but it is maybe going to snow or mix, somewhere or everywhere, in the forecast area and possibly up to 20” and maybe more).

K :|Adequate/Satisfactory Forecast:

For local forecasts, the forecasted accumulation range was essentially correct or insignificantly high or low at the peripheral of the forecasted accumulation ranges (forecasted accumulation range falls completely within or mostly within the verification accumulation range, i.e. ranges overlap significantly) in some geographical areas but in the entire forecast region the verification accumulation range was significantly non-symmetric, and/or skewed and was significantly different than the forecasted accumulation range in some geographical areas, or in large forecast geographical regions with large disparities where the verification accumulation range was significantly non-symmetric and/or skewed and in both/either instance(s) the verification accumulation mean was near or within the forecasted accumulation range, or the forecasted accumulation range is significantly different but still to some extent intersects (ranges overlap, normally <= 40% but not < 25%) with the verification accumulation range, not including local extremes or anomalies.

OR

A narrative contingency forecast (local or regional) recognized, mentioned, and included as a forecasted possibility or probability, an unspecified accumulation amount in a specific geographical area(s), either above or below the actual forecasted accumulation range, and the verification accumulation mean or range is consistent with the narrative and reasonable but no specific contingent accumulation range was forecasted.

OR

A narrative contingency forecast (local or regional) recognized, mentioned, and included as a forecasted possibility or probability with a specific accumulation range and geographical area(s), either above or below the actual forecasted accumulation range, that was verified by a mean within the contingent forecasted accumulation range or a contingent forecasted accumulation range is significantly different but still to some extent intersects (ranges overlap, normally <= 40%) with the verification accumulation range, not including local extremes or anomalies.

OR

The forecast narrative (local or regional) explicitly indicated areas of the forecast geographical area expected to get much higher or much lower accumulations that would require expanded forecast accumulation ranges outside the normal guidelines and significantly invalidated the mean accumulation or range intersection criteria but is nevertheless, consistent, understandable, and fairly reasonable, though not representative relative to the forecasted accumulation range and/or the contingent forecasted accumulation range and is significantly outside the upper and/or lower boundaries of the contingent forecasted accumulation range. This is necessary to avoid penalizing an accumulation forecast required to follow guidelines within certain forecast limits when there is a large spread of accumulation data in the verification range. Guidelines are used to restrict forecast accumulation ranges, contingent accumulation ranges, or local/isolated ranges based on the expected accumulation  over the forecast area, otherwise, all encompassing wide ranges could be used making all accumulation forecasts of little value (i.e. An expected snowfall of 10” is expected; if no guidelines and limits are placed on the main, contingent and isolated/locally range accumulations, the forecast could read T-20”, isolated 20”+, possible 0-10” with mixing, which tells use basically nothing but it is maybe going to snow or mix, somewhere or everywhere, in the forecast area and possibly up to 20” and maybe more).

L :( Unsatisfactory, Inaccurate/Busted forecast:

For all forecasts (local or regional), in all or nearly all geographical areas regardless if the verification accumulation range in some or all geographic areas was significantly non-symmetric and/or skewed or if the verification accumulation range was mostly symmetric, uniform, or mostly non-skewed; the forecasted accumulation totals are significantly higher or lower than the forecasted and contingent forecasted accumulation ranges. The forecasted accumulation range and/or if applicable , the narrative contingent accumulation range, either above or below the actual forecasted accumulation range, were essentially incorrect (forecasted accumulation range falls completely outside the verification accumulation range, i.e. ranges fail to overlap) and the verification accumulation mean falls significantly outside the forecasted accumulation range, not including local extremes or anomalies.

The original accumulation forecast or the narrative contingent accumulation forecast fails to meet the standards defined for an accurate or satisfactory forecast as outlined above.

Hurricane Information

Glossary of National Hurricane Center (NHC )Terms: https://www.nhc.noaa.gov/aboutgloss.shtmlExternal Link

Information on Hurricanes:

Although I have a general and specialized education on tropical systems, including tropical cyclones and their causes and effects, I do not have an in depth working knowledge and application of tropical meteorology including tropical cyclones nor do I claim to be an expert on tropical and subtropical systems, cold core/warm core systems nor developing systems in either a barotropic or baroclinic atmosphere. On the contrary, my expertise lies more with research in desert and cold weather/arctic atmospheric profiling.

Hurricanes are very difficult to monitor and track with complete accuracy. Even with the equipment we have today some assumptions, parameterizations, and a thorough analysis of many factors are still needed to display the information gained from reconnaissance missions in a useful way. There are several different ways to measure wind speeds in a hurricane. Originally and still today for tropical depressions and storms, data is collected by aircraft at the 700 MB level (~10,000 feet) and surface wind speeds are calculated to determine a surface wind speed from various ratios derived from past empirical data. This is surely not an exact method but does provide an “in the ballpark” estimate of surface wind speeds especially as storms (cyclones) are developing and strengthening. Normally an estimation of 80-90% of the 700 MB wind speed is used. As tropical storms intensify into hurricanes GPS dropsondes and WP3D Stepped Frequency Microwave Radiometer (SFMR) are used. While dropsondes are very accurate (within several MPH) they are expensive and only about 15-20 are used during any Hurricane Hunters mission leaving many unobserved areas to be filled in by expert severe weather analysis teams. SFMR uses certain frequencies to measure microwave radiation from the ocean surface. Using some assumptions about the atmosphere they gather what is called an ocean surface brightness temperature and then a calculation of wind speeds can be obtained from a linear assumption of wind speed and corresponding brightness. In high wind scenarios these methods don’t always give the same results although they are usually fairly similar. Severe weather experts must determine, for that particular storm, what represents the most accurate measurement based on a number of parameters and most importantly the internal dynamics of the storm that are constantly changing. There are parametric and dynamical approaches to forecast a wind distribution field in hurricanes. There are the data intensive dynamical models the National Hurricane Center prefers and several parametric models (each has their benefits depending on the storm) that can quickly forecast a wind distribution field almost as well as the dynamical approach and much more quickly.

Finally, The Cyclone Global Navigation Satellite System (CYGNSS), to measure reflected GPS satellite signals from low orbit to monitor storm wind speeds from space was launched in December 2016. Hurricanes are very difficult to monitor and track with complete accuracy. The following applies in every instance as it pertains to winds in a hurricane (Northern Hemisphere):

1. The strongest winds in most areas of a hurricane are normally found at about 300-500 meters ABOVE the surface unaffected by surface friction.

2. Winds officially reported as sustained winds are obtained by several methods, a 10 minute average or one, sometime two, minute average and are measured at ~33 feet (10.1 meters) ABOVE the ground in an unobstructed location.

3. The strongest winds in a hurricane are found in the right side, especially the right forward quadrant (assuming you are in the northern hemisphere).

4. The winds in the right side are not only stronger but extend much farther out as does the entire field of tropical storm winds (winds >39 MPH).

5. The strongest winds in the left quadrant are about 20% and possibly 25% weaker than the right side.

6. The winds in the left side diminish much quicker as you move away from the eye wall.

7. The strongest winds normally occur about 15 miles (can occur between 6 and 30 miles) from the center of the eye.

8. Winds can decrease up to 30% in just 15 miles (if the max winds are 6 miles from the center of the eye) and by more than 40% just 30 miles from the center of the eye, especially as it applies to the left side where winds diminish more quickly with distance.

9. Winds can drop by 50% or more just 60 miles from the center of the eye and at 60-70 miles from the center can be just 40-50% of the maximum winds for that quadrants eye wall, especially as it applies to the left side where winds diminish more quickly with distance.

10. Other meteorological parameters, wave height and direction, coastal geographical features etc. can affect wind speeds dramatically, especially as a storm moves over land (friction), loses strength due to wind shear, dry air, cooler water etc. and a number of other factors and begins or continues to deteriorate.

Finally, while estimates can be made it is impossible to determine the dynamics and resulting effects in every area covered by the hurricane. Each hurricane is unique unto itself and its properties are affected by forces internally and externally. Wind speeds are ever changing with the internal dynamics and external forces and the sampling of data covers very small portions of the hurricane leaving experts to “fill in the blanks”. As stated previously there are also many algorithms used based not only on physical data but also on assumptions and parameterizations. NOAA (National Hurricane Center) will almost always use a dynamical approach when tracking and forecasting hurricanes through use of dynamical atmospheric and ocean models. These models can used independently (i.e. GFS, ECMWF) or coupled/linked with an ocean model (i.e. GFDL, GFDN, HWRF) to better represent ocean/atmospheric interaction.

Which models suck and why?

Numerical weather prediction is extremely complex! Here is a simplified list of all of the aspects of NWP forecasts:
-mathematical formulation of the PDEs that govern the atmosphere (typically called “model dynamics”)
-treatment of sub-grid scale processes (depends on the model resolution, typically called “model physics” or “parameterizations”)
-initial and lateral boundary condition data
-model configuration (horizontal and vertical resolution, finite difference or spectral, time step, vertical coordinate, number of soil levels or ocean levels, topography)
-post-processing

Things you need to understand about each model to really get an idea how it should differ from other models
Model dynamics
-Which schemes are used to discretize the equations? Leapfrog? Adams-Bashforth? Forward Euler? Backward Euler? Each one has known strengths and weaknesses.
-What order of truncation was used for each scheme? Higher order schemes generally give better results, but also increase computational expense.
-Is this model using finite differencing to represent the derivatives or is it using Fourier series and waves to represent the fields?

Physics parameterizations
-Which sub-grid scale processes are being parameterized? Deep convection? Shallow convection? cloud/rain physics? boundary layer? land surface? urban surface? sub-surface? radiation?
-For each process that is being parameterized, which scheme is being used? For example, there are about 3 or 4 different cumulus parameterization schemes that operational forecast models use. Some are well documented and their strengths and weaknesses well known, while others are new or are improved versions of well known schemes but haven’t been rigorously verified or documented. For some schemes, no documentation exists at all (it was written and maintained by one person). Keep in mind that although Weisman et al. (1997) is typically cited as the paper that said you don’t need to use convective parameterization starting at 4 km grid spacing, but convective processes are not resolved at 4 km! The entire range between about 1 km and 10 km is a gray zone where conventional convective parameterization schemes used in many modern forecast models are not meant to be used, but deep convection is still not fully resolved. It’s inaccurate and unfair to call 4 km models “convection-resolving”, because they aren’t.

Initial and lateral boundary condition data
-This is where the meat of the PDF that Rob linked to falls. The amount, type, and quality of data ingested and processed by data assimilation schemes must be known. Also, there are different types of data assimilation (3DVAR, 4DVAR, EnKF etc.), and different configurations within each type of assimilation. There are also different ways of taking irregularly spaced data and transforming it to a gridded array (Cressman, Barnes etc.). Many of these are well documented and have known strengths and weaknesses (advantages/disadvantages), but you need to know which model system uses what.
-Global models don’t need lateral boundary condition data, but “limited area” models like the NAM, RAP, HRRR, SREF etc. do. Limited area model output is strongly correlated with the skill of the model that provided the lateral boundary conditions past a certain forecast hour (depending on the size of the limited area model domain). Also, how was the lateral boundary condition data used? Was it only applied to the outermost grid point? The outer 5? Was it filtered at all?

Model configruation
-Horizontal resolution is big, obviously. But one thing many people tend to overlook is the vertical resolution. Back in the day when grid spacings were tens of kilometers, grid columns were wide and short, as the vertical resolution was much finer than the horizontal resolution. Vertical resolution hasn’t increased nearly as much as horizontal resolution has. In convection-allowing models today, the grid columns are much skinnier than they used to be, as individual grid boxes are much taller than they used to be. This impacts how processes such as convection are treated.
-Vertical coordinate: while the model output you see on websites is generally given on isobaric surfaces, NWP models generally do not use an isobaric or fixed height vertical coordinate. Most models use a terrain following sigma or eta vertical coordinate, or an isentropic one (the RUC used a hybrid isentropic-sigma coordinate).
-Topography: when you setup a WRF run, you can select the quality of the topography that the model assumes. This is hugely significant when considering processes impacted by interaction with the Earth’s surface.
-Is the model strictly an atmospheric model (having only grid points within the atmosphere)? Many climate models are actually “Earth system” models that include grid points in the soil and under water, and include dynamics and physics parameterizations to prognosticate soil temperature, soil moisture, SST etc.

Post-processing
-As mentioned before, the output you see on a website is not the raw model output. Rather, the output was post-processed from the native model levels to isobaric or iso-height surfaces. There are different ways to interpolate vertically.
-Was there a post-processing scheme or method used to alter the raw model output to either correct for known biases in the model or to force ensemble output to fit a Gaussian distribution? This is especially important when viewing output from ensembles. Also keep in mind that while you can find “CAPE” as a field to view in model output, you should determine if it’s surface-based, mixed-layer, most-unstable, or some other level CAPE. Some websites don’t distinguish between those types. Also, did they use the virtual temperature correction? The GFS didn’t until a few years ago. Not sure about anything else.

As MClarkson said, you can compile your own error statistics by obtaining a large sample size to determine any deficiencies or particular strengths of a model. However, to really know, you’ll need to know every aspect of the model to be sure. Also, keep in mind that error statistics are heavily quantitative, yet Rob asked questions like “GFS always has systems that are too fast/slow”, which is much more qualitative, and isn’t easily addressed by examining basic error statistics. This is because you are crossing the line between pure quantitative statistics and into feature-based identification, which computers are much farther behind compared to how they do with pure quantitative statistics

Jeff Duda https://stormtrack.org/community/threads/which-models-suck-and-why.27598/#post-321381External Link

Many thanks to Jeff DudaExternal Linkfor that extremely detailed and helpful information on climate models! -Mike

Forecasts 2021

*** WEATHER UPDATE*** METMAN WEATHER SERVICES 4 Apr 2021 9:00 AM EDT Philadelphia Metro Area BRAVES GAME FORECAST (1-4 PM)

After a brief upper air disturbance causes some overnight clouds and AM sprinkles skies will mostly clear and high pressure will continue to dominate most of the day bringing mostly sunny skies with a few intermittent afternoon clouds and somewhat breezy at times with a high of 66.

Game time forecast is mostly sunny with and temperatures upper 50s to mid 60’s across the metro area. Winds will be from the NW at 5-15 MPH G22 increasing throughout the day. Max 6 hr (2 PM – 8 PM) 10 meter AGL wind gust is 26 MPH. Winds likely left field across to right field possibly more in from left as the game progresses.

*** WEATHER UPDATE*** METMAN WEATHER SERVICES 3 Apr 2021 1:25 PM EDT Philadelphia Metro Area BRAVES GAME FORECAST (4-7 PM)

High pressure will dominate most of the day bringing mostly sunny skies with some afternoon clouds and very low humidity. A WNW breeze will be much more tolerable.

Game time forecast is for mostly sunny to partly sunny skies with increasing clouds and temperatures ranging 50-55° across the metro area. Winds will be from the WNW at 6-12 MPH with occasional slightly higher gusts. Max 6 hr (2 PM – 8 PM) 10 meter AGL wind gust is 18 MPH.
Winds likely left field across to right field but significantly weaker than Thursday.

Sunday Intermittent periods of clouds and sun, High 65, Winds NW 8-14 MPH G23 Max 6 hour G27 . Game time temperatures upper 50’s to mid 60’s

*** WEATHER UPDATE*** METMAN WEATHER SERVICES 3 Apr 2021 10:40PM EDT Philadelphia Metro Area BRAVES GAME FORECAST

High pressure will dominate most of the day bringing mostly sunny skies with some afternoon clouds and very low humidity. A WNW breeze will be much more tolerable.

Game time forecast is for mostly sunny to partly sunny skies with increasing clouds and temperatures ranging 50-55° across the metro area. Winds will be from the WNW at 6-12 MPH with occasional slightly higher gusts. Max 6 hr (2 PM – 8 PM) 10 meter AGL wind gust is 18 MPH.
Wind likely left field across to right field but significantly weaker than Thursday.

Sunday Mostly sunny followed by intermittent periods of clouds and sun, High 65, Winds NW 8-14 MPH G21 Max 6 hour G27 . Game time temperatures upper 50’s to mid 60’s

***QUICK WEATHER UPDATE*** METMAN WEATHER SERVICES 1 APR 2021 2:10 PM EDT Philadelphia Metro Area Opening Day BRAVES GAME FORECAST

Not much change in the forecast. Game period temperature should be right around 50 with NW winds of 15-20 MPH, occasionally slightly higher. Most larger gusts should be in the 25-30 MPH range but a few could exceed 30 MPH. Max 6 hr (2 PM – 8 PM) 10 meter AGL wind gust from the 00Z ECMWF Hi-Res model is 32 MPH.

*** WEATHER UPDATE*** METMAN WEATHER SERVICES 31 MAR 2021 9:20 PM EDT Philadelphia Metro Area Opening Day BRAVES GAME FORECAST for 4/1/2021

An upper level trough will provide the impetus as a cold front pushes through the Philadelphia area tonight bringing .25″-.5″” of steady rain that will transition to more light showery precipitation on Thursday morning. This will usher in much cooler air and blustery conditions for Thursday.

Game time forecast is for partly sunny skies and temperatures ranging from the mid 40’s to low 50’s across the metro area. Winds will be from the NW at 15-25 MPH with occasional gusts to 35 MPH possible. If my orientation is correct, that would be mainly in from left field to slightly across left to right. Chances of precipitation are low but a few sprinkles or a very light brief shower are possible with the upper air instability.
Note: Max 6 hr (2 PM – 8 PM) 10 meter AGL wind gust was derived from the  00Z ECMWF Hi-Res model. The latest 12Z run is just slightly less at 33 MPH.

Saturday Mostly Sunny, High 55, Winds W-NW @ 6-12 MPH Max G22. Game time temperatures in the low 50’s.
Sunday Partly Cloudy, High 63, Winds W-NW @ 8-12 MPH Max G28. Game time temperatures mid 50’s to low 60’s

Dec 16-17, 2020 Winter Storm

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

***WEATHER UPDATE*** METMAN WEATHER SERVICES In Storm Update: 12/16/20 8:45 PM EST HARRISBURG, PA REGIONAL FORECAST

Due to exceedingly strong warm air advection the sleet has moved into the central zone and southern portions of the NW forecast zone and remained longer than anticipated. Unless heavier bands overcome this occurrence, which may occur in some areas, therefore, accordingly the storm totals are adjusted slightly downward. Also, the depth of the warm air advection aloft has allowed the precipitation to fall to the ground before refreezing as sleet so periods of freezing rain will also be occurring in some areas.

Local South Central PA forecast:

The three forecast zones (SE, central, NW) for this storm run on a general line from SW to NE. The SE 1/3 of the forecast area runs from route 30 near York to Lancaster and to the SE. The central 1/3 of the forecast area is east and south of the I81 corridor to the SE zone. The NW forecast area is to the west and north of the I 81 corridor.

A mix of sleet/snow pellets/freezing rain is likely Wednesday evening in the SE zone for 4-6 hours, in the central zone possibly for 3-5 hours, and intermittently for 3-4 hours in the southern areas of the NW zone. Some freezing rain is possible, especially south, but should not exceed 0.15″ accumulation.

The SE zone can expect 5-10″ locally up to 12″. The central zone can expect 10-15″ locally up to 18″, especially near the I81 corridor. The NW zone can expect 15-20″, locally up to 24″. Winds will generally be 10-15 MPH with possible gusts of 25-30 MPH in western areas and 15-20 MPH with 35-40 MPH gusts in eastern areas on Wednesday evening and overnight. Near blizzard conditions are possible at times in southern York county and in southern and eastern Lancaster county.

Point Forecasts:

Harrisburg 13″ (11.2″ official), ratio 9:1
Lancaster 9″ 7.1″
York 11″ 7.6″
Chambersburg 12″
Carlisle 15″
Lebanon 12″ 9.7″
New-port 19″

***WEATHER UPDATE*** METMAN WEATHER SERVICES Final Pre Storm Forecast: 12/15/20 10:15 PM EST HARRISBURG, PA REGIONAL FORECAST

Synoptic Overview, Model and Forecast Discussion:

Models are leaning to some mixing, especially to the SE part of the forecast region but also a bit into the central areas to the east and south of the I81 corridor. Current model projections for Quantitative Precipitation Forecast QPFs are likely to be 1.6″ ± .2″.

A marginal warm air advection layer above and below 1 km will likely introduce some snow pellets and sleet in the southern 1/3 of the forecast area, especially SE. This will reduce accumulations somewhat in those areas, especially south of Route 30 and east of York, but some brief periods of sleet/snow pellets are possible briefly at times Wednesday evening as far north as the I81 corridor.

Expect snow ratios to average ~10:1 less to the SE and higher to the NW as max temps in the thermal profile are expected to be in the mid 20’s to low 30’s over most of the area and in the upper 20’s to mid 30’s in the SE areas. Areas with colder air aloft to the NW of the I81 corridor will accumulate mostly snow but sleet/snow pellets may mix in briefly at times near the I 81 corridor Wednesday evening. The current forecast track shifted the heaviest areas of snowfall slightly to the NW increasing accumulations to the NW and decreasing accumulations in SE areas.

A dry slot (lull in precipitation) in the central and eastern parts of the forecast area is still possible Wednesday evening. It’s also likely that several mesoscale bands of heavy CSI snowfall aligned parallel to the thermal wind vector will affect some areas. These bands are typically 50-100km wide. A 200 MB jet streak of 125-150 kts and strong lower level winds will also favor the likelihood for the heavy banding snowfall. Add warm air advection and isentropic lifting and you can get 2-3″/hr of heavy snow. Thundersnow is possible, especially in the NW and central parts of the forecast region as areas of traditionally convective instability (CI) pass through. CI will always override CSI. The peak period for these bands will likely be from 8 PM Wednesday until 2 AM Thursday.

Local South Central PA forecast:

Expect snow to arrive late morning to early afternoon in most areas. Snowfall rates in the early/mid afternoon will generally be 1″/hr or less, increasing to 1″-2″/hr late afternoon and early evening and then 1″-2″ or more at times Wednesday night into early morning hours of Thursday. Most snowfall should exit by daybreak Thursday with a few light snow showers or flurries adding just a coating to an inch of accumulation.

The three forecast zones (SE, central, NW) for this storm run on a general line from SW to NE. The SE 1/3 of the forecast area runs from route 30 near York to Lancaster and to the SE. The central 1/3 of the forecast area is east and south of the I81 corridor to the SE zone. The NW forecast area is to the west and north of the I 81 corridor.

The event will start as snow for all and then switch to a mix or all sleet, especially the SE zone, for a while before back to snow before ending by daybreak Thursday morning. The location will determine the duration of sleet, generally briefly to nonexistent in the NW zone and of longer duration as you move farther to the SE. The mix will affect the NW forecast area very little, the central forecast zone somewhat but heavy snow banding will most likely overcome any reduction by sleet in that area. The most affected area due to mixing will be the SE zone along a line from York to Lancaster and points to the SE.

A mix of sleet and/or snow pellets is likely Wednesday evening in the SE zone for 2-4 hours, intermittently in the central zone possibly up to 2 hours in more southern areas of this zone, and briefly for up to an hour in the southern areas of the NW zone. Some freezing rain is possible, especially SE, but should not exceed 0.1″ accumulation.

The SE zone can expect 6-12″ with isolated higher amounts. The central zone can expect 12-18″ locally up to 22″ in a few areas near the I81 corridor. The NW zone can expect 16-22″, locally up to 24″.  Winds will generally be 10-15 MPH with possible gusts of 25-30 MPH in western areas and 15-20 MPH with 35-40 MPH gusts in eastern areas on Wednesday evening and overnight. Near blizzard conditions are possible in southern York county and in southern and eastern Lancaster county.

Point Forecasts:

Harrisburg 13″
Lancaster 9″
York 11″
Chambersburg 12″
Carlisle 15″
Lebanon 12″
New-port 19″

***WEATHER UPDATE*** METMAN WEATHER SERVICES Initial Pre Storm Forecast: 12/14/20 8:30 PM EST HARRISBURG, PA REGIONAL FORECAST
Synoptic Overview, Model and Forecast Discussion:

Most models have been pretty consistent with the timing of the storm although accumulations have varied from 8-12″ up to 20-26″. Current model projections for Quantitative Precipitation Forecast QPFs also cover a wide range from .9″ to 2.1″ throughout the forecast area. A reasonable model blend indicates 1.4-1.8″ QPF indicating a 14-18″general accumulation for south central PA assuming a 10:1 ratio. RH levels from the surface to 500 MB are fairly well saturated.

A marginal warm air advection layer from .75 km -3 km is possible in the southern and SE areas on Monday evening. This may reduce accumulation somewhat in some areas to the SE, especially south of Route 30, but some brief periods of sleet/snow pellets are possible briefly at times Wednesday evening as far north as the turnpike. At this time the dendritic growth zone is insufficient in depth to significantly enhance snowfall amounts.

Expect snow ratios to average ~10:1 – 12:1 as max temps in the thermal profile are expected to be in the low to mid 20 over most of the area and in the upper 20’s in the southern and SE areas. This could lead to a fluffier 12:1 ratio snow and higher accumulations for most of the forecast areas adding an additional 3-5″ of accumulation except for the more southern and SE areas. The colder thermal profile to the north and warmer to the south/SE and possible mix to the S and SE are clearly being picked up by the NAM and European model thus perhaps overemphasizing the affect on snowfall accumulations in both areas. There is no doubt enhanced snowfall will occur in areas with colder air aloft.  The current forecast track puts south central PA into central eastern PA in the area of maximum potential snowfall (but that could trend slightly north) as cold air will be in place and an increasing negative tilted upper level trough. Energy from this trough will transfer to a developing low off the SE coast late Tuesday and rapidly intensify on Wednesday as it approaches the DELMARVA area. This will be a classic nor’easter as it intensifies Wednesday night but the heavier winds will likely remain east of the local forecast region. This will be a relatively fast moving system with the greatest snowfall occurring between early afternoon Wednesday and the early morning hours on Thursday.

Current unknowns such as dry slots, exact path of the developing low, definitive QPF’s and corresponding snow ratios, warm air advection in the 1-3K layer (as of now this event should be mostly snow in south central PA but I can’t rule out warm air advection mixing in southern areas, especially SE near the MD border east of the river) and the exact location of any deformation bands/mid level instability and frontogenesis, and other convective areas that could deposit heavier snow account for a wider range of the forecasted accumulation. Of particular interest is the possibility of a dry slot or wedge of warm air that could move a bit farther north in the lower Susquehanna Valley into areas east and south of the I 81 corridor. and turn the precipitation to more sleet, and maybe some freezing rain. Either would greatly reduce accumulations in that area.

Local South Central PA forecast:

Expect snow to arrive late morning to early afternoon in most areas. Snowfall rates in the afternoon will generally be 1″/hr or less, increasing to 1″-2″/hr in the early evening and then 1″-2″ or more at times Wednesday night into early morning hours of Thursday. Most snowfall should exit by daybreak Thursday with a few light snow showers or flurries adding just a coating to an inch of accumulation.
Expect general accumulations of 12-18″ with localized areas up to 22″ in central and northern areas while 8-14″ is more likely in the SE tier east of the river where warmer max temperatures aloft and possible mixing may occur. Generally, somewhat higher accumulations is expected in the northern, central and east central portions of the Harrisburg forecast region although some areas farther south, especially western areas could also see accumulations in this range. A possible mix of sleet and/or snow pellets, and less likely freezing rain for several hours or more on Wednesday evening in the SE areas of the forecast region could reduce snowfall amounts by 2-6″, especially near the MD border. Winds will generally be 10-15 MPH with possible gusts of 20 MPH in western areas and 10-20 MPH with 25-30 MPH gusts in eastern areas on Wednesday evening and overnight.

Forecasts 2020/Hurricane Isaias

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

 

*** WEATHER UPDATE*** 24 Sep 2020 2:40 PM EDT Atlanta Metro Area Metman Weather Services BRAVES GAME FORECAST

Synopsis:
Moisture remnants from TS Beta have been integrated into an upper level trough and will bring rainfall to the Atlanta area today into Friday morning. Models differ somewhat on the amounts but are in general agreement on the timing. The GFS is minimizing the rainfall indicating .5″ or less total rainfall and only about .1″ during game time. However, the Euro and HRRR high resolution models have been consistent with total rainfall of at least .5″ and in some cases 1″ or a bit more. I tend to agree with that for a number of reasons. I expect .1″- 25″ during game time tonight. The HRRR is now trending lower in game time rainfall (<.2″) on the latest runs. I expect mostly steady light to occasional moderate rainfall this evening and overnight. A few localized rumbles may occur but instability indicators are not impressive. I still expect .5-1″ or a bit more in the Atlanta Metro Area today into Friday morning. Heavier rain bands could bring 1.25″ or more in some areas, especially, but not exclusively, to areas north of the metro area and the NE mountains. There may also be some areas between the heavier bands that get less than .5″ of total rainfall but those should be minimal. In any event it is going to be a fairly dreary, soggy day, evening and overnight in the Atlanta Metro area. Clearing should begin Friday afternoon as the remnants from TS Beta dissipate bringing party cloudy skies for Friday evening.

Today
Intermittent light to moderate rain early this afternoon and after a late afternoon/early evening lull, intermittent showers will become more continuous later this evening (after 8 PM) but mostly light with occasionally moderate and possibly briefly heavy at times this evening and overnight. About .25″-.5″ is expected this afternoon, another .1″-.25″ this evening through game time and another .25″-.5″ overnight. Rain will wind down tomorrow morning. Generally, total rainfall amounts for the event expected to be between .5-1″ or a bit more in most places. Higher amounts possible to the N/NE but a few local areas could experience rainfall of less than .5″ and some in excess of 1.25″ depending upon exactly where the locally heavier bands materialize. Temperatures in the mid 60’s to low 70’s with ESE winds 6-12 MPH with higher gusts.

For game time period expect mostly light to occasionally moderate showers and a rumble of thunder possible. The heaviest rain tonight is likely later tonight and into the early morning hours so there is a bit more positive news about rainfall amounts during the game but it’s still likely at least light rain will be falling most of the time. Total rainfall during the game time period is expected to be .1″-.25″ but has been trending lower from .2″-.4″ on the earlier model runs. Winds will be ESE at 8-12 MPG with gusts to 20.

Friday
Early morning showers then clearing Friday afternoon with a few light showers or sprinkles possible. Some instability may cause a few isolated showers but most of the activity is associated with an upper air disturbance and should be confined to areas south and east of the Atlanta metro area more in central GA. High temperature will be in the the mid to upper 70’s. Game time temperature in the mid 70’s falling to the low 70s. Unless upper air trends change from current expectations, there is only a slight chance of a brief shower. Generally light W/NW winds at 3-6 MPH.

*** WEATHER UPDATEE*** 23 Sep 2020 3:30 PM EDT Atlanta Metro Area Metman Weather Services BRAVES GAME FORECAST

Synopsis: Generally cloudy but favorable weather tonight under the influence of a high pressure ridge but as the ridge breaks down moisture from TS Beta will overspread the area on Thursday and into Friday. Rainfall totals are a bit less than previously thought on Monday because the expected path of Beta and the remnants has changed slightly. Expect .5-1″ of rain in the Atlanta Metro Area Thursday into Friday but some a slight deviation with the remnant moisture could bring up to 2″ or more of precipitation in some areas, mainly to the areas north of the metro area in northern GA. Clearing should begin Friday afternoon as the remnants from TS Beta dissipate bringing party cloudy skies for Friday evening.

Tonight
Should be a good night for a game. Mostly cloudy skies with a game time temperature in the upper 60’s to low 70’s. Temperatures should dip just into the mid 60’s tonight by 10/11 PM. A few sprinkles are possible. Light winds.

Thursday
Intermittent showers move into the area later Thursday morning and persist throughout the day becoming more continuous and just occasionally intermittent in the afternoon and evening and extending overnight into Friday morning. A rumble of thunder is possible but no severe weather is expected. Temperatures will remain fairly steady throughout the day in the mid 60’s to low 70’s. Looks unlikely for a Thursday night game at this time.

Friday
A few morning showers with a light shower possible in the early afternoon then gradual clearing through the afternoon with partly cloudy skies and temperatures in the low to mid 70’s at game time and dipping to 70 or just below later in the evening. Generally light winds.

***WEATHER UPDATE*** Atlanta Metro Area 21 Sep 2020 4:25 PM EDT Metman Weather Services BRAVES GAME FORECAST

Looks like a nice evening for baseball. Clear to partly cloudy skies with temps starting in the mid 60’s at game time and dipping into the upper 50’s by 10/11PM. Winds will be ESE at 5-10 MPH for the game period with a few higher gusts possible early and gradually decreasing as the game moves along. This equates to a cross wind from left field to right field if I’m looking at the field position correctly. Today through Wednesday looks good but currently it looks as if remnants from TS Beta will bring 1-3″ of rain Thursday and Friday and unsettled weather for the weekend. I’ll check that out more tomorrow and Wednesday.

*** Weather Update*** 28 Aug 2020 3:20 PM EDT Philadelphia Metro Area Metman Weather Services BRAVES GAME FORECAST

A few showers and isolated thunderstorms in the Philadelphia area later this afternoon and evening. Complicated dynamics involved with a nearby stationary front, an upper level disturbance with high vorticity (i.e. counterclockwise rotation) passing through central PA and central NJ later this afternoon and a moist (PW ~2″) unstable environment. Stability indicators are also a bit up hinting at the possibility of isolated severe weather with these storms. Severe weather is currently making its way through Central PA heading to the SE. Storms are moving at a pretty good clip ~35-40 MPH. The possibility also exists that these storms will become less intense this evening and more scattered as the the vorticity max wanes early this evening as they approach the Philly area but too soon to tell. I would say that is a good possibility although some scattered showers are still likely to be in the area for a while after game time. Considering the propensity to postpone games, tonight’s is very questionable. Global and regional models including the NAM seem to want to hold most of the rain off until tomorrow but HRRR is indicating .25-5″ in the Philadelphia area late this afternoon with possible isolated heavy downpours of 1″ or more. NAM is generally more favorable with only 1.” or less leading up to game time and little rain during game time. Waiting on the NAM 18Z and later HRRR runs to get a better handle. I’ll check the radar later to see how it looks.

Looking at Saturday FOX day game at 1 PM the cloudy, unstable conditions will persist and the influx of moisture from Laura will make for showers and a few thunderstorms. A frontal passage late Saturday should make for a nice day Sunday although a but of upper level instability may still exist and create some puffier cumulus clouds but subsidence will likely cap development and any shower activity and it should be a pretty fair day.

***WEATHER UPDATE*** Atlanta Metro Area 26 Aug 2020 2:30 PM EDT Metman Weather Services BRAVES DH GAME FORECAST

Temps in the mid to upper 80’s, dew points in the the mid 70’s, and little wind is going to make for a very muggy day/evening in the Atlanta Metro area. Precipitable Water (PWAT) values are declining but still significant over north central GA. Isolated to widely scattered showers will be in the periphery, especially at the far N/NE tier of GA but the Atlanta metro itself should remain dry for the most part barring an isolated shower or thunderstorm as the ridge of high pressure continues to expand westward. The best chance for any showers in the Atlanta metro area would be later this afternoon or early this evening. Model QPF’s (quantitative precipitation forecast) are unimpressive today and this evening in the Atlanta metro area, (0 to <.1″) although Hi-Res (HRRR) and NAM/NAM-3k to a certain extent but not as heavy, are indicating scattered showers, some localized and heavy (HRRR), to the east and north of the Metro area between 1 and 5 PM. It’s possible a shower could sneak into the area. I’ll check the radar later to see if anything is near the ballpark.

Note: Remnants of Laura are expected to be in the mid-Atlantic states this coming weekend and combined with a projected stationary front and cold front passage on Saturday expect scattered showers and thunderstorms, some heavy, with the enhanced moisture feed from Laura. This could affect the game with the Phillies on Saturday.

 

***WEATHER UPDATE*** Atlanta Metro Area 25 Aug 2020 4:15 PM EDT Metman Weather Services BRAVES GAME FORECAST

Showers over the northern GA tier have been persistent but intensity has decreased and rain is now mostly light/very light in the Atlanta metro area. These persistent showers will continue to slowly lift northward over the next several hours while decreasing in coverage and intensity and are expected to clear the metro area by 6 PM. A very light rain/mist could persist a bit longer into the evening with insignificant accumulation. It will remain cloudy with winds generally less than 5 MPH and temps will max out in the mid to upper 70’s with dew points in the low 70’s so it will be very muggy for tonight’s game. As mentioned in my earlier update a residual shower or two and/or a rumble of thunder is possible but so far it’s looking good for the game time period. At this time any significant new development is unlikely. A brief downpour is possible but becoming more unlikely. Models generally showing a rain free evening. GFS is hinting at some light shower activity. I’ll check the radar after dinner.

 

***Northern GA forecast (Tuesday)*** 25 Aug 2020 9:35 PM EDT Metman Weather Services

Extensive showers and scattered thunderstorms are expected in central and northern GA on Tuesday from Marco. Radar shows a line of showers, with locally heavy downpours approaching the Atlanta metro area. Abundant tropical moisture (PWATS in excess for 2″) will continue to spread northward over the state. While the temperatures will be moderated it will feel very muggy. Cloud cover on Tuesday will once again reduce the chance for severe weather but scattered thunderstorms and heavy downpours will occur in many spots this morning and likely into the early afternoon. Models indicate a general .5-1″ over central and northern GA today. Some areas will receive less than .5″ with other getting 1-2″ or more. The heaviest precipitation in northern GA is expected in the western and central areas. The Atlanta metro area and surrounding areas will likely be a focus of the heavier showers over the next several hours and maybe into the early afternoon hours also.

Game time forecast remains unchanged as most of he activity is expected to have moved well north but considering the air mass showers may be around and a brief downpour is still possible.

Yesterday and overnight southern and central GA generally received .75-1″ with quite a few spots reporting 1-2″. There were several isolated reports of ~3″ in south central and SE GA.

***GA/Braves Game Forecast (Monday-Tuesday)*** 24 Aug 2020 2:35 PM EDT Metman Weather Services

Extensive showers and scattered thunderstorms expected Monday and Tuesday from Marco as abundant moisture (PWATS in excess for 2″) will spread northward over the state. Cloud cover on Monday will reduce the chance for severe weather and numerous thunderstorms. Generally heavier rainfall will be in central and southern GA on Monday with the northern areas only expected to generally receive ~.25″ or a bit more in some spots. Isolated locally higher rainfall amounts in northern GA on Monday are possible also. In southern and central GA, rainfall amounts of .5-1″ will be common with some areas picking up 1-2″ or more. Several wedges of higher precipitation are possible into central and eastern GA. On Tuesday rainfall shifts northward as a general .5″ is expected across central and northern GA, especially the northern third of the state, with areas of heavier precipitation above 1″ and other areas less than .5″. Models are in pretty good agreement that most of the rainfall in northern GA should occur overnight Monday and in the morning hours of Tuesday and improving conditions with more widely scattered showers in the afternoon and winding down by the evening hours. Game time forecast is for improving conditions Tuesday night. The worst should be over by game time but some residual showers and a heavy thunderstorm or downpour could still be around.

 

*** WEATHER UPDATE*** 4:25 PM EDT 22 Aug 2020 Metman Weather Services BRAVES GAME FORECAST

The upper air low/trough is weakening and moving NE as the Bermuda high ridge extends westward. PWATs are lower than the last several day reflecting less moisture throughout the vertical profile. Once again cloud cover in many spots across the northern GA tier will limit diurnally-driven convection activity later today and tonight. Current coverage and intensity is somewhat less than yesterday so it’s unlikely that any leftover afternoon showers and storms will be a significant problem for tonight as they should be dissipating by 7 PM. but some showers could be in the vicinity. Isolated showers this afternoon with rainfall accumulations generally .25″ or less though a few locally heavier showers may occur. Severe weather indices today are unimpressive.
For game time, regional mesoscale models are in fair agreement of isolated showers with .2″ or less (mostly less) tonight. HRRR and other sources indicate that a localized heavier shower or two over northern GA can not be ruled out. Any showers that develop later tonight are expected to occur mostly to the north of the Atlanta metro area. Overall, looks to be favorable for tonight’s game. I’ll check radar before the game and post an update.

 

*** WEATHER UPDATE*** 3:45 PM EDT 21 Aug 2020 Metman Weather Services BRAVES GAME FORECAST

Unsettled weather continues over the Atlanta area. An upper level trough has developed into an upper air low and a marginal jet streak over southern GA will lead to a NE movement of the low tomorrow. That low will continues to provide a SW flow providing plenty of moisture, especially at lower levels today (PWATS-precipitable water are ~1.5″).

For today, extensive cloud cover in many areas and slightly drier air in the mid levels will limit diurnally-driven convection activity later today and tonight. Disturbances in this SW flow will produce mostly isolated shower activity but a few localized areas or bands of showers are possible as are some stray isolated thunderstorms. This afternoon several areas could accumulate .25-.5″ but most areas will be less than that. Later today and tonight may see a few isolated areas of locally heavier rainfall but severe weather indices (i.e CAPE, lapse rate, shear and lifted index) are marginal although there could be some brief gusty winds, especially if the sun can provide that energy in a few places. Regional mesoscale and high resolution models are in fair agreement of .2 or less (mostly less) tonight. The biggest caveat in all of this is the lack of solar insolation to ignite convective activity. Lacking that solar forcing makes conditions a bit more stable in most areas. Any large bands or convective complexes are not expected at this time but given the moisture laden low level atmosphere and possible small disturbances aloft in the SW flow some bands of showers or a few storms are possible at times tonight and overnight. A pop up heavy shower or storm is possible with the current dynamics but would be isolated in nature. Generally speaking for game time I think it looks to be favorable except for a few isolated shower areas and maybe a few stray storms.

*** QUICK WEATHER UPDATE*** 6:59 PM EDT 19 Aug 2020 Metman Weather Services BRAVES GAME FORECAST (Game POSTPONED at 7:10 PM (the original game time))

A line of moderate to heavy showers is passing through the Atlanta vicinity. The heaviest rain is still expected to the north. The good news is that the line continues to move east and has diminished in intensity and coverage over the last 45 minutes. The heavier showers should be over by 7 PM with mostly light intermittent showers after that until maybe 8. If we’re lucky and little to no development occurs with or behind this line we could wait this out a little and still play but probably not until at least 8 or 8:30 PM with the grounds crew work. They may not want to wait that long. I would say only about .1″ is expected after 7 PM so it’s looking better than 45 minutes ago for sure.

*** WEATHER UPDATE*** 6:15 PM EDT 19 Aug 2020 Metman Weather Services BRAVES GAME FORECAST

A line of showers has developed and expanded just west of the Atlanta vicinity. These showers are slowly moving east. It appears the heavier showers may arrive a bit earlier than previously anticipated. Look for light to moderate to heavy showers to begin between 6:15-6:30 PM. This line may last several hours before completely clearing so tonight’s game is becoming doubtful. The HRW and HRRR models may have been on target. I’ll check back in shortly to monitor the radar.

*** WEATHER SYNOPSIS/UPDATE*** 4:45 PM EDT 19 Aug 2020 Metman Weather Services BRAVES GAME FORECAST

Unsettled weather over the Atlanta area for the next 2-3 days. An upper level trough combined with a deep moisture column i.e. moisture laden SW flow, PWATs (precipitation water) generally 1.5-1.75″, and diurnal heating will support widespread convective activity and support numerous showers and thunderstorms today through Saturday. Strong upper level winds with the possible development of an upper level low Friday into early Saturday will continue to enhance the showers and storms.
For today and this evening expect areas of showers and thunderstorms with isolated severe weather a possibility, especially north and west. Most storms today should be nearer to the axis of the upper level trough (i.e. north and west) but certainly scattered showers and a storms could develop and affect the Atlanta Metro area tonight but I expect most heavy activity to stay to the north and west at least until 9 PM when things could pick up a bit. Considering the proximity/axis of the upper level trough to the Atlanta vicinity some additional development is possible in the evening also in addition to any storms already in progress. Activity should begin winding down after 10 PM in most areas. Overall most models (global and regional models) are projecting .25″ or less during the game period but several HRW mesoscale models develop strong convection over the area with abundant rainfall exceeding .5″ and the NAM-3km has been persistently aggressive with heavy rainfall in the area. I generally prefer the High-Resolution Rapid Refresh Model-HRRR (a derivative of the HRW) as we get closer to actual occurrence of an event (it updates hourly) but anytime the HRW models indicate areas of heavy precipitation it bears watching. The most recent HRRR 19Z is growing more aggressive with heavier rainfall also. It’s still a bit early to have full confidence but worth watching closely to see what the 20Z run shows. HREF (High-Resolution Ensemble Forecast) also sinks the .1-.25″ precipitation area into the Atlanta vicinity. I’ll check the radar as we approach game time to see how things are developing.

Forecasted severe weather parameters (NAM and HRRR) for tonight

Surface Based CAPE (750-1500 j/kg) Weak to Moderate SBCAPE (Surface-Based Convective Available Potential Energy) is a measure of instability in the troposphere.

Lifted Index (-3 to -5) Moderate (Lifted Index-LI) is an indice used to assess low level parcel (in)stability of the troposphere.

Mid Level Lapse rate ~5 Moderate (over 6 is High ). A lapse rate is the rate of temperature change with height. The faster the temperature decreases with height, the “steeper” the lapse rate and the more “unstable” the atmosphere becomes.

Isolated strong storms with heavy rainfall possible with some damaging winds possible. Chances of anything more severe is very low.

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Isaias Recap *** METMAN WEATHER SERVICES 10 Aug 2020 3:35 PM EDT

Severe Weather…
Aside from the initial severe weather associated with landfall in NC, Isaias spawned tornadoes in VA, MD, DE, NJ, and PA.

Rainfall totals from Isaias:

Rainfall totals were generally in the range forecasted, however, heavier rainfall totals of 3-6″ isolated areas to 8″ extended north into eastern MD, northern DE and into eastern PA. Forecast was for 2-4″ isolated 6″ north of VA. This was likely due to a better organized and defined storm and strength gained by attaining hurricane status for several hours before and after landfall.

Forecast….Storm surge of 3-4′ for 50-75 miles on either side of landfall is likely.
Storm surge:
Myrtle Beach, SC 4.2′ 32 miles
Wilmington, NC 4′, 40 miles
Wrightsville, NC 3.2′, 43 miles
Georgetown, SC 3′, 74 miles
Beaufort, NC 2.8′, 115 miles

Forecast….35-45 MPH or more sustained winds with gusts to 60 MPH or more in some areas just north of landfall
Wind Gusts:
Wrightsville Beach, NC 86 MPH, 43 miles NE
Wilmington, NC 74 MPH, 40 miles NE
New River, NC 63 MPH, 76 miles NE
Cedar Point, NC 61 MPH, 95 miles NE

Forecast…25-40 MPH sustained winds with 50-60 MPH winds gusts north of the storm center as she progresses NE.
While sustained winds in some areas were a bit higher most areas were in the forecasted range. Wind gusts tended to be in range but some areas on the eastern side of the storm had gusts to over 70 MPH as Isaias tracked northward even into New England where maximum Massachusetts wind gusts of 61-63 MPH were reported.

End Recap

Isaias Update*** METMAN WEATHER SERVICES 4 Aug 2020 11:25 AM EDT

Isaias made landfall as a Category 1 hurricane at 11:10 p.m. EDT Monday near Ocean Isle Beach, North Carolina, just to the northeast of Myrtle Beach, South Carolina, with maximum sustained winds of 85 mph. Isaias attained CAT 1 status several hours before making landfall and was downgraded to a tropical storm in the early morning hours on Tuesday. Path now is just slightly west of the last update. Isaias is currently tracking just east of Baltimore and will pass just west of Philadelphia soon. Several outbreaks of severe weather in NC in the right forward quadrant (i.e. NE side) as Isaias approached landfall and moved inland. Otherwise, forecasted winds and rainfall amounts are being realized as expected as she tracks to the NNE at 35MPH and increases in forward speed. Isaias will continue to move NNE and exit into Canada near midnight tonight.

Isaias Update*** METMAN WEATHER SERVICES 3 Aug 2020 5:35 PM EDT

Tropical Storm Isaias continues to track NNE at ~16 MPH. Isaias will continue to move NNE/NE as she moves through SC, NC, VA and up the east coast. Isaias is still on track to make landfall late Monday night between Myrtle  Beach, SC and Southport, NC, most likely still a tropical storm. Isaias could briefly reach a weak CAT 1 status prior to landfall but that’s doubtful. Storm surge of 3-4′ 50-75 miles on either side of landfall is likely. Rainfall totals, wind speeds and track deviate little from my previous updates although a few areas near the storm track could get 6-8″ amounts in SC, NC and VA and points north of VA will generally be 2-4″ with isolated areas up to 6″ areas.

Isaias Update*** METMAN WEATHER SERVICES 2 Aug 2020 11:15 AM EDT

Isaias continues to move NW at 8-9 MPH. The slower speed has allowed Isaias to move slightly farther to the west than previously forecasted and will come very close or possible touch the coast in central Florida. Isaias is now a tropical storm and is not expected to reach hurricane status again. Isaias’s path will slowly shift to the NNW and then eventually to the NE as she approaches the Carolinas and interacts with the upper level trough. Isaias will likely make landfall in central/northern SC, maybe near Myrtle Beach late Monday or early Tuesday. A southern NC landfall is still a possibility. Isaias’s forward speed will gradually increase today and then continue to increase as she turns to the NE. Because of the slight shift in path Isaias is now likely to remain slightly inland after landfall as she continues NE through NC, VA, NJ and into New England. This will provide strong gusty winds and heavy rains to those areas. If the inland path comes to fruition the rainfall in coastal areas north of SC will be significantly reduced as the heavier rains are likely to be more inland. If Isaias’s path does turn slightly east off the coast, winds and rainfall will be enhanced in the coastal areas.
As Isaias moves along the Florida coast today and into early Monday, tropical storm winds are possible near the coast and rainfall of 1-3″ with 3-5″ or more in some areas near the central Florida coast. As Isaias continues to the NE expect 1-2″, isolated 2″+ along coastal GA. Eastern SC could receive 4-8″ and 2-6″ of rainfall is expected as she moves to the NE. This will be accompanied by 35-45 MPH or more sustained winds with gusts to 60 MPH or more in some areas just north of landfall and 25-40 MPH sustained winds with 50-60 MPH winds gusts north of the storm center as she progresses NE. After landfall winds will rapidly decrease on the western side of the storm as you move father from the center of the storm. The decrease in wind speed is much more gradual on the eastern side and can increase for several hundred miles before decreasing.

Isaias Update*** METMAN WEATHER SERVICES 1 Aug 2020 10:05 AM EDT

Isaias continues to move NW and the speed has slowed slightly to 12 MPH. While the slowing is good for a future path away from coastal areas it allows the storm to create heavier rain and wind impacts in the near future. Isaias’s future path will shift slightly east as she interacts with an upper level trough making expected landfall slightly farther north and a bit later than previously expected, possibly on the southern coastal area of NC. As expected, Isaias continues to be disorganized with no clearly distinguished eye/eyewall, most likely due to an infusion of dry air and wind shear aloft. Isaias will continue to encounter dry air and shear in the near future keeping the system disorganized and hindering any significant escalation of intensity. HereExternal Link  is a view of the dry air being infused into Isaias and the dry air it will encounter in its path. In Florida, Isaias’s impact is now likely to be felt Sunday into Monday with waves of 10-12 feet, possible storm surge, tropical force winds/wind gusts, and 2-4″ of rain with isolated higher amounts in extreme eastern areas, especially central Florida. The heaviest rain is still projected to be off the coast. Isaias will likely make landfall in southern NC as a tropical storm and continue NE near the coastline. The right forward quadrant with the most severe weather will come into play briefly if Isaias makes landfall expected sometime Monday PM or Tuesday AM. 2-6″ of rain or more is possible in central and eastern SC and NC while 1-2″ is possible in SE GA. A South Carolina impact is still possible and if the storm moves more slowly than expected Isaias could turn to the NE earlier and avoid landfall all together. While tropical storm Isaias will be much less intense after landfall, 50-60 MPH wind gusts and heavy rainfall of 2-6″ or more could still affect parts of southern VA, DE, eastern MD, NJ and southeastern NY and eventually southern and eastern New England.

Isaias Update*** METMAN WEATHER SERVICES 31 JUL 2020 3:45 PM EDT

Isaias continues to track NW at ~15MPH through the Bahamas and will eventually veer N/NNE as it skirts Florida and moves up the coast. Warm Atlantic ocean temperatures helped strengthen the storm in the near term but shear and land interaction will inhibit future growth. Isaias has developed into a weak CAT 1 hurricane in an area of low shear and warm waters but significant intensification is not likely. A Saharan Air Layer (SAL) in Florida also contradicts intensification. Several inches of rain are possible in some areas of eastern Florida as Isaias tracks northward. At this time it appears that Isaias and the heavier rains will remain off the coast of Florida but a small drift in the path cold put parts of eastern Florida into stronger tropical storm and briefly but unlikely hurricane force winds and more severe weather and much heavier rain. The current data indicates the path to remain just off the Florida coast but an upper level trough will not push it quite as far east as anticipated yesterday and it’s likely to make landfall as a weak CAT 1 storm somewhere in central SC to southern NC. Some severe weather is now expected as Isaias makes landfall and 2-6″ of rain or more is possible in central and eastern SC, NC, and VA. The right forward quadrant with the most severe weather will come into play briefly as Isaias makes landfall in SC/NC as a weak Cat 1 or strong tropical storm, likely sometime Monday PM but intensity/winds will drop rapidly upon making landfall.

Isaias Update*** METMAN WEATHER SERVICES 30 JUL 2020 4:55 PM EDT

Current spaghetti plots are continuing to move Isaias father east as it tracks NW and then veers N/NE. Warm Atlantic water temperatures will help strengthen the storm in the near term but shear and land interaction will inhibit future growth. There is also a bit of a Saharan Air Layer (SAL), a dry, hot layer of air with dirt, sand, and dust. This mid level atmospheric event causes a temperature inversion and suppresses convective development. To strengthen, Isaias would have to overcome the elements of this environment, an unlikely task. It still bears watching as it will pass very near the Miami area sometime Saturday and possibly very near the coast of North Carolina Outer Banks maybe late Monday or early Tuesday. Tropical force winds could affect parts of the eastern coast of southern Florida are less likely in NC. Current information keeps enhanced precipitation off the coast in southern Florida but 2-5″ is possible in parts of eastern NC. The right forward (i.e. strongest) quadrant looks to stay east of coastal areas minimizing the most severe weather to coastal areas. This storm bears watching as a slight deviation in the current path could alter the future path and provide enhanced winds and precipitation, especially to areas in southern and central Florida. Barring blocking atmospheric conditions such as strong inverted troughs or high pressure ridges, climatology and historical analogs often push these storms to the N/NE. Current indications are that Isaias will develop into a strong tropical storm and may attain CAT 1 status. The majority of information currently available projects a tropical storm or weak CAT 1 hurricane at most with CAT 2/3 very unlikely, especially as it nears the Florida coast.

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***Final Storm Totals*** Sun Jan 19, 2020 Harrisburg, PA (posted 9:49 AM EST)

Liquid precipitation .35″
Snow 1″

***In Storm Update*** Sat Jan 18, 2020 1:05 PM EST Harrisburg, PA Vicinity

Model QPF’s are in good agreement and have lowered a bit on the latest runs. Still expecting ~.4″ total QPF. NAM guidance is now elevating temperature over the freezing mark by early evening so if anything falls after 7 PM it will be just drizzle. Transition to sleet has already occurred to some places west of Harrisburg and will occur shortly over most of the area over the next several hours. Expect sleet initially and then a wintry mix and possibly a little freezing rain/drizzle on top of everything later this afternoon and maybe early evening. A few cold pockets could still see some freezing drizzle early this evening. Things begin to wind down significantly by 6 PM, effectively ending nearly all accumulating precipitation. Total snow/sleet accumulation unchanged at C-3″. Generally at the higher end of the range to the N/NE and the lower end of the range farther to the S/SW of Harrisburg. Most of the area should see 1-2″ No change in other aspects of the forecast.

 

***Final Weather Update*** Friday Jan 17, 2020, 8:30 PM EST Harrisburg, PA Vicinity

Discussion:

Most models are trending just a bit wetter so QPF’s have been adjusted up .1″, otherwise, good model agreement despite the global models, especially the GFS, continue to struggle with the warm air advection (WAA) aloft  and have somewhat elevated snowfall accumulations. NAM guidance continues to hold in the cold air at the surface, so accordingly, I would be remiss if I didn’t mention that temps at the surface may remain at or below freezing early Saturday evening in a few spots that could produce some very light freezing drizzle into the evening hours but I believe most areas will move above the freezing level by early evening. Snow accumulations will likely be significantly hindered by sleet and maybe some freezing rain in the afternoon and early evening depending on the exact height and depth of the warming layers and then eventually changes to mostly light rain/drizzle or light freezing rain/freezing drizzle, depending on when the surface temperature rises above freezing at any particular locality, by late afternoon/early evening as surface temperatures creep just above the freezing level. Any ice accumulation will be limited as any precipitation during this time is expected to be very light drizzle. A few areas, especially to the south, but really almost anywhere, could get up to a .1″ ice glaze in the late afternoon and early evening. Be wary of this especially if you are in a valley or low lying area where cold air pools. Models are now in good agreement with total QPF (quantitative precipitation forecast, i.e. liquid equivalent expected for event). Model average QPF’s are in the .5″± .1″ range with only about 25-50% expected to fall as accumulating snow/sleet. Assuming a 10:1 ratio, and that would be generous, that would put general overall snowfall totals in the C-3″ range, possibly 4″ in some spots north of the I81/78 corridor and east of Carlisle. Little change in snow accumulations from my previous updates. Most localities in south central PA should be in the 2-3″ range generally with slightly more to the N/NE (3-4″), and slightly less to the S/SW (C-2″). While not expected, worth mentioning is that a delay of WAA arrival by just several hours could elevate snowfall totals (re: weather event 15-16 Nov 2018 when most were forecasting 2-6″ max and the WAA delayed entry dumped nearly 9″ on Harrisburg aided by several hours of heavy snow bursts before sleet arrived) and WAA arriving a little earlier than expected could slightly lower accumulations and provide for more sleet and freezing rain/drizzle before surface temperatures warm after sunset. While the example from Nov 2018 above won’t happen in this event (there is not enough available moisture, QPF’s were well over 1″ for the 2018 event), it does demonstrate the affect on snowfall accumulations involved with the timing of WAA.

Snow should start to spread across south central PA in the early to mid morning hours (7-10 AM) from SW to NE, with some snow/sleet in the afternoon as surface temps remain cold and warm air advection aloft begins and then a winter mix (snow/sleet/ freezing rain-drizzle) for a short time before changing to mostly drizzle in the evening. As previously mentioned, a few spots may have freezing drizzle in the evening. Intermittent light rain/drizzle could persist until the early morning hours of Sunday (most accumulating precipitation should end by mid evening) and may end with a few flurries or light snow showers in some areas. Sunday will see temperatures drop with the highs likely to be in the mid to upper 30’s sometime in the early morning hours and falling throughout the day as a brisk W/WNW wind at 10-20 MPH with gusts to 30 MPH ushers in the cold air. High Sunday afternoon will be in the low to mid 30’s.

***Weather Update*** Jan 16, 2020 7:05 PM EST (revised 9:30 PM EST) Harrisburg, PA Vicinity 

Not much has changed from my previous commentary except that the models trended a little warmer, especially with warm air advection aloft, changing the precipitation to sleet, freezing rain, and rain and reducing accumulation.

Most models are trending somewhat warmer and picking up on more significant warm air advection earlier in the afternoon on Saturday on the latest runs, 12Z and 18Z. Any snow or freezing precipitation should be confined to the daylight hours with drizzle, possibly mixing with freezing drizzle in a few colder areas, moving in after dark as surface temps also warm slightly. Models waver somewhat on snow amounts depending on atmospheric thermal profiles varying with the exact timing of warm air advection (WAA) aloft. Global model QPF projections are on point but tend to over-exaggerate snowfall amounts a bit with WAA so the mesoscale models are likely closer to the actual snowfall accumulation and this forecast is weighted with that on mind. Temperatures aloft and at the surface will support snow in the AM hours but eventual warm air advection (WAA) aloft will cause the snow to change to snow/sleet then snow/sleet/freezing rain and eventually probably all rain (more likely mostly drizzle) as the temperature warms. The track and movement of the surface low passing to the NW and the supporting upper air dynamics will determine the exact timing of events.

Snow should start in the early to mid morning hours with some sleet early afternoon as surface temps remain cold and warm air advection aloft begins and then a winter mix as more warm air advection above and below the 850 MB level (~ 5000 ft) works its way in later in the afternoon. This warm air advection will cause a significant temperature inversion (warming with height) aloft from ~3K-8K ft. Snow falling through this area will be warmed and eventually some will melt as the warm layer deepens. The resulting rain will then refreeze in the shallow layer of cold air near the surface (3k ft and below) and fall as sleet mixing with some snow. If the layer is too shallow (later in the afternoon) to refreeze it will fall as freezing rain mixing with some snow as long as the surface temperature remains below freezing.

Snow accumulation will likely be significantly hindered by sleet in early/mid afternoon depending on the exact height and depth of the warming layers and then eventually changes to light rain/drizzle or light freezing rain/freezing drizzle, depending on when the surface temperature rises above freezing at any particular locality, by late afternoon/early evening as surface temperatures creep just above the freezing level. Ice accumulation from freezing rain is expected to be minimal but .1″ max of ice could accumulate in a few areas, especially south, during the afternoon hours. Light drizzle and possibly some isolated freezing drizzle at times in some areas, since the surface temperatures are somewhat marginal early evening, should end by mid evening but could linger until midnight or the early morning hours on Sunday in spots and end with a few light snow showers/flurries in the early morning hours.

Based on current NAM guidance, temps at the surface may remain at or below freezing so some areas could have some very light freezing drizzle into the evening hours but I believe most areas will move to or above the freezing level by early evening. Any ice accumulation will be extremely low as any precipitation during this time is expected to be very light. Weighted ensemble model average QPF’s are in the .4″± .1″ range with only about 25-50% of that falling as accumulating snow/sleet. Assuming a 10:1 ratio that would put general overall snowfall totals in the C-3″ range, possibly 4″ in some spots north of I81/78 corridor.  Still a bit of time for that to change a little depending on the exact track of the low, timing of the warm air advection and timing of surface warming.

***Weather Update*** Jan 13, 2020, 9:45 PM EST Harrisburg, PA Vicinity 

For the event expect Saturday, most models are trending colder on the latest runs, 12Z and 18Z, and pushing the precipitation back a bit, mostly during the daylight hours on Saturday. Pretty good model agreement. Could now be mostly snow with some mixing late as a bit of warm air advection from the 850 MB level (~ 5000 ft) to the surface works its way in during the very late afternoon/early evening. At the current time, 4-6″is not out of the question but still early.

Hurricane Laura Aug 2020

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

From the National Hurricane Center (8/27/20)…

“Laura made landfall near Cameron, Louisiana, around 0600 UTC (1 am CDT) with maximum sustained winds of 130 kt, which is near the high end of category 4 status. At the time of landfall, Laura was a ferocious looking hurricane with a clear circular eye, an intense eyewall, and tightly-coiled surrounding spiral bands. Since the powerful hurricane has been inland for a few hours, there has been some decrease in winds, and the estimated initial wind speed based on Doppler radar data, surface observations, and guidance from an inland decay model is 105 kt.”

Notes:
Cameron, LA is ~30 miles SSW of Lake Charles, LA and 37 miles east of Port Arthur, TX
Cat 4 Hurricane  = 113-136 kt, 130-156 mph
130 kt = ~150 MPH
4 AM CDT winds = ~120 MPH

***Laura Update (final update before landfall)*** 26 Aug 2020 3:45 PM EDT Metman Weather Services

Hurricane Laura continues to track NNW now as a CAT 4 hurricane and is forecast to continue to intensify somewhat as it moves through the warm northern Gulf waters. Laura is still forecast to make landfall sometime early Thursday morning near the TX/LA border (i.e. between Port Arthur/Beaumont, TX and Lake Charles, LA). Laura has turned to the NW/NNW a tad earlier than expected and will veer N Thursday after landfall. Laura will encounter shear and possibly an eyewall replacement cycle limiting further intensity before landfall. Nevertheless, Laura is expected to hit the LA/TX coast with fury and the devastating effects of a powerful CAT 4 hurricane. 
Laura will bring damaging high winds in excess of 135 MPH with possible gusts to 160+ MPH, severe weather, 30′ waves, extensive flooding of up to 10′ or more over flood levels and a dangerous storm surge of 8-12′ in eastern TX and southern LA, and possibly up to 15′ or more in some areas in LA on the east side of the storm. Storm surge is possible 20-30 miles inland. Upon landfall Laura will lose strength rapidly but still bring drenching rains and flash flooding as she continues northward through LA and AR on Thursday and Friday and then turns ENE/E into Kentucky and VA on Saturday before exiting into the Atlantic late Saturday or early Sunday. Rainfall amounts of 4″-12″ in extreme SE TX and western half of LA are expected within 50-75 miles of Laura’s path with heavier rain extending farther east. Heavy rains of 4-8″ or more are expected along its path farther inland throughout eastern TX, western LA, AR, and possibly into SE MO, southern IL, and western KY. Isolated localized amounts of 8″ or more are possible. As Laura turns to the E through KY expect 1-4″ with localized higher amounts to 6″, especially in the western areas, and 1-3″, isolated 4″ amounts as she moves through/near West VA, extreme southern Ohio, southwestern PA and central/northern VA, MD/DE and exits into the Atlantic where Laura could then re-intensify.

 

***Laura Update*** 26 Aug 2020 9:30 AM EDT Metman Weather Services

Hurricane Laura continues to track NW now and is forecast to continue to intensify and as it moves through the warm Gulf waters with little resistance. Laura is still forecast to make landfall sometime early Thursday morning near the TX/LA border (i.e. Port Arthur/Beaumont, TX). Laura has turned to the NW and will veer NNW by Wednesday afternoon and nearly N by Wednesday night. Conditions for further intensification in the near term are favorable with low shear and Laura is now forecast to reach Cat 4 status Wednesday afternoon before encountering shear before landfall and returning to CAT 3. Laura should now make landfall as a CAT 3 hurricane bringing damaging high winds in excess of 115 MPH with possible gusts to 135+ MPH, severe weather, 30′ waves, extensive flooding of up to 10′ or more over flood levels and a dangerous storm surge of 8-12′ in eastern TX and southern LA, and possibly up to 15′ in some areas in LA on the east side of the storm. Upon landfall Laura will lose strength rapidly but still bring drenching rains as she continues northward through LA and AR on Thursday and Friday and then turns ENE/E into Kentucky and VA on Saturday before exiting into the Atlantic late Saturday or early Sunday. Rainfall amounts of 4″-12″ in SE TX and western LA are expected within 75 miles of Laura’s path with heavier rain extending farther east. Heavy rains of 4-8″ or more are expected along its path farther inland throughout eastern TX, western LA, AR, and western KY. Localized amounts of greater than 8″ are possible. As Laura turns to the E through KY expect 1-4″ with localized higher amounts, especially western areas, and 1-2″, isolated 3″ amounts as she moves through central/northern VA.

 

***Marco (final update) and Laura Update*** 25 Aug 2020 2:25 PM EDT Metman Weather Services

Marco has no significant convective activity and is now classified as a post-tropical remnant low pressure system. Marco will continue to track westward along the LA coastline and gradually dissipate.

Hurricane Laura continues to track WNW and is forecast to continue to intensify as it moves through the warm Gulf waters. Laura is still forecast to make landfall early Thursday near the TX/LA border (i.e. Port Arthur/Beaumont, TX) but the continued WNW track before turning to the NW could push landfall just slightly to the west of that somewhere between Beaumont and Houston. As discussed in the last update, the expanding Bermuda high will keep Laura moving to the WNW in the near term and eventually turning to the NW tonight and then NNW by Wednesday afternoon and N by Wednesday night. Laura is expected to continue to strengthen today and could reach CAT 2 status by early Wednesday morning. Conditions are favorable for further intensification and Laura is now forecast to reach Cat 3 status Wednesday before encountering shear near landfall. Laura should make landfall as a very strong CAT 2 hurricane although maintaining CAT 3 status upon landfall is very possible also. Laura will bring damaging high winds in excess of 100 MPH with gusts to 125+ MPH, severe weather, extensive flooding of 4-8′ or more over flood levels and a dangerous storm surge of 8-12′ in eastern TX and southern LA. Upon landfall Laura will continue northward through LA and AR on Thursday and then turn NNE/NE/E into the lower Ohio Valley Friday and Saturday and exiting into the Atlantic late Saturday or early Sunday. Rainfall amounts of 4″-12″ in SE TX and western LA are expected within 75 miles of Laura’s path and 1-4″ on the periphery of each side, especially east. After an initial decrease in intensity after landfall Laura could strengthen somewhat later Thursday bringing heavy rains of 2-6″ or more along its path farther inland throughout eastern TX, western LA and western AR. Localized amounts of greater than 6″ are possible. As Laura turns to the NE expect 1-4″ with localized higher amounts, especially western areas, through the lower Ohio Valley and 1-2″, isolated 3″ amounts as she moves through the mid-Atlantic.

 

***Marco and Laura Update*** 24 Aug 2020 2:15 PM EDT Metman Weather Services

Marco has decreased significantly in strength with just 50 MPH sustained winds and is expected to continue to weaken. Coincidentally, the upper trough with the strong SW flow aloft that has been persistent in the southeast has created shear that is tearing apart the storm at the upper levels and moving the areas of rainfall and thunderstorms to the NE side of Marco. Landfall expected this evening in eastern LA as a weak tropical storm and it will turn westward into drier air and be downgraded rapidly to a tropical depression. All wind and surge warnings for the Gulf coast associated with Marco have been discontinued. This is good news for LA and points west. Abundant moisture from Marco will travel NE into AL and GA creating numerous showers, some heavy, and a few scattered thunderstorms today and tomorrow.

Laura continues to track WNW and is forecast to intensify as it moves through the warm Gulf waters and encounters minimal vertical shear. The upper trough and its associated shear is expected to extend westward as Marco moves west opening up a path for Laura to turn slightly more to the north Wednesday with landfall expected in western LA very late Wednesday or early Thursday morning. The expanding Bermuda high will keep Laura moving to the WNW in the near term with eventually turning to the NW and then NNW by Wednesday afternoon. Models aren’t in total agreement over the intensity but Laura is expected to strengthen slightly later tonight and could reach hurricane status quickly on Tuesday as she moves over the warm gulf waters with insignificant shear and favorable upper level conditions. It’s possible that Laura could reach Cat 2 status and possible, but improbable at this time, that it could reach major hurricane, Cat 3, status before landfall with damaging high winds, severe weather, flooding and a dangerous storm surge. Current projections indicate a strong Cat 1 hurricane with winds possibly in excess of 90 MPH and winds gust to 105 MPH.

 

***Hurricanes Marco and Laura Update*** 22 AUG 2020 11:00 AM EDT Metman Weather Services 

Hurricanes Laura and Marco are continuing their paths toward the Gulf of Mexico and will likely make landfall in the middle of next week. The path for both storms has tracked more westerly with Marco expected to make landfall in Texas, south of Houston, sometime late Tuesday and Laura is expected to make landfall in Louisiana Wednesday afternoon. It’s possible some interaction may occur but the probability of merging is very small. It’s more likely that the the stronger hurricane will continue and the other one will weaken or if both storms are relatively close in strength then both storm will most likely weaken. This interaction could upset the timing and position of landfall for both storms, and cause some veering to the east for Marco and west for Laura. In nearly all cases storms passing close to each other ultimately have a detrimental affect on both storms. It’s also possible that one or both storms may deintensify before these events can unfold. Should be an interesting scenario to follow next week.

Forecasts 2019

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

***Quick Weather Update*** Metman Weather Services Thursday Sep 12, 2019, 6:15 PM EDT Philadelphia, PA Vicinity BRAVES GAME FORECAST

Good News! The shower activity moved through a bit earlier than anticipated with just some very light rain wrapping up and there is currently very little radar activity upstream. Should get nothing more than a few light intermittent showers, if that. Just a small chance of a brief heavier shower.

***Weather Update*** Thursday Sep 12, 2019, 4:05 PM EDT Philadelphia, PA Vicinity BRAVES GAME FORECAST

A cold front pushing through the area will provide some showers and a possible T-storm in the Philly vicinity later this afternoon and early evening. Cloud cover should inhibit any severe weather but a brief gusty shower is certainly possible. Most of the activity should occur before the game, however, some light showers could stick around a bit longer and a few intermittent light showers could linger into the evening. It wouldn’t be surprising to see a short delay in the start of the game. Models are in pretty good agreement with generally less than .1″ throughout the game time period, most of them early in that time period. I’ll check the radar later to monitor those showers moving through and if any heavier showers develop. Temps generally in the 70’s with ENE to NE winds about 10 MPH (that’s blowing in from RF if my orientation is correct).

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***QUICK WEATHER UPDATE*** 6:35 PM EDT 14 Aug 2019 Metman Weather Services BRAVES GAME FORECAST
Current estimate of arrival of showers and storms is now about 6:45- 7:00 PM. Intensity is waning somewhat now but could still have some pretty good moderate or even heavy showers for about 10 minutes and it won’t completely push through until after 7:15. Could get .1-.25″, probably in the lower end with the decrease in intensity. Likely a delay in the start of the game. My best guess would be about 7:45-8:00 PM for first pitch if everything remains static with intensity waning and movement.

***QUICK WEATHER UPDATE*** 5:35 PM EDT 14 Aug 2019 Metman Weather Services BRAVES GAME FORECAST
Several isolated shower/thunderstorm cells have developed into a line to the NW of Atlanta (just N/NW of Cartersville) and are moving towards the Smyrna vicinity. Current estimate of arrival is between 6:30-7:00 PM if they hold together, and it looks like they will but maybe not with quite the same intensity as they are now. They are moving pretty fast and at this time would only last about 20 minutes with some thunder and lightning and some gusty winds. A brief heavy downpour of about 10 minutes is possible. The high resolution model is more optimistic and has them weakening before arrival in the area. Could cause a delay in the start of the game.

P.S. I’m really not familiar enough with the area but these showers could be orographically induced and weaken rapidly as they move SE. Are there mountains in the Cartersville area and to the NW of that?

*** WEATHER UPDATE*** 4:05 PM EDT 14 Aug 2019 Metman Weather Services BRAVES GAME FORECAST

Radar looks good in northern GA. The frontal boundary responsible for the precipitation after midnight last night has sunk to the south over southern GA. Looks like we’re in for a pretty decent evening, although warm and humid, with tempos in the high 80’s to near 90 for game time and dropping into the low 80’s by 11 PM. Models in agreement for a rain free evening but an isolated pop up shower can’t be ruled out. More later.

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***WEATHER UPDATE*** 6:55 PM EDT 13 Aug 2019 Metman Weather Services BRAVES GAME FORECAST
Not much as changed from the previous update. Radar still very inactive in the Atlanta metro area (a small cell NW of Canton). 18Z GFS still holds on to 1.-.2″ during game time. Certainly possible with the isolated activity around but I believe most of the Atlanta metro area and especially, NW of Atlanta, remain mostly dry with just a light sprinkle or shower possible (<.1″). Areas farther N and E and even some areas to the S are more at risk for isolated to scattered showers as we get after the 10 PM time frame.

****WEATHER UPDATE**** 4:35 PM EDT 13 Aug 2019 Metman Weather Services BRAVES GAME FORECAST

Radar in the greater Atlanta metro area and surrounding areas is pretty much devoid of echoes at this time. A frontal boundary to the north will likely cause some precipitation in extreme northern and some eastern area of GA later tonight. Regional and high resolution models are looking good for the game this evening keeping the showers and storms to the north and east. An isolated storm or shower is possible.The global GFS want to bring in some showers but I believe the 18Z run will lower or eliminate most of those showers. I’ll do a more in depth look later and take a look at the latest model runs and radar after dinner.

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*** Weather Update*** 10:55 AM EDT 4 Aug 2019 Atlanta Metro Area Metman Weather Services BRAVES GAME FORECAST
Clouds and showers over north central GA may inhibit diurnal convection early this afternoon and somewhat delay the development of shower activity. An upper air low (trough) and with several disturbances could create enough instability to trigger a few showers but looking like most shower activity will become active a bit later in the afternoon/early evening, after 3 PM, due to the lack of surface heating. The timing of the activity depends on the exact position of the upper level trough, timing of the upper level disturbances, and amount surface heating. My best guess at this time is that any activity will be delayed until late this afternoon or early evening. That doesn’t discount some possible isolated activity in the mid afternoon time frame but does make it a bit more unlikely in my opinion. Models indicate .1″ or less throughout the game time frame. I’ll take another look at the situation after lunch.

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***Quick Weather Update*** 7:15 PM EDT 2 Aug 2019 Atlanta Metro Area Metman Weather Services BRAVES GAME FORECAST
Showers and storms not nearly as widespread or heavy as last night and models are indicating .1″ or less through the game time period. Just an isolated shower or thunderstorm is possible throughout the entire Atlanta metro area with just a small chance of large scale shower and storms developing. We should get this one in tonight.

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***Weather Update*** 10:51 EDT 1 Aug 2019 Metman Weather Services BRAVES GAME FORECAST
Showers continue to be moderate to somewhat heavy as we are on the western edge of the slow stubborn area of heavier showers. The showers are maintaining intensity as they slowly drift NE but I am also seeing some redevelopment and intensification, not unexpected, of echoes to the south and west back over the ballpark area once again. Also, more showers and some development is taking place to the SW. Whether this game is completed largely depends on the weakening of the current showers and the movement and the ability of that area of showers to the SW to maintain intensity over the next several hours. As of this time we’re about 50/50 or slightly less of resuming play at some point. If we’re not seeing a weakening of the activity withing the next 30-45 minutes the likely hood of finishing this game diminishes greatly.

***Weather Update*** 10:18 PM EDT 1 Aug 2019 Atlanta Metro Area BRAVES GAME FORECAST

An upper air trough and some outflow boundary driven development this evening with weak winds aloft, and abundant moisture makes for slowing moving storms and heavy showers/thundershowers. Most of these will develop, rain hard for a while and then eventually weaken leading to some heavy downpours and possible isolated areas of flash flooding. Looks like the current cell has expanded to a larger area of rain and is moving slowly to the NE. Looks like the moderate to heavier rain will hang around until about 10:30 PM and then weaker precipitation should occur as the cells weaken and continue to move slowly to the NE. Additional development is possible after that but after midnight activity should stat winding down. Models indicate a general total rainfall of about .3″-.6″ and more (maybe an inch or more) in areas affected by multiple heavy downpours. Severe weather indicators aren’t overly impressive but a few isolated severe storms could also be mixed in at times over the next several days.

There is a good chance this activity of afternoon and evening showers and storms will continue through most of the weekend or even into next week.

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23 Jul 2019 10:30 AM EDT Metman Weather Services Washington DC area weather
Update on Nats game postponed due to heavy rain and possible severe weather:
Dulles had .5″ between 1 AM and 2 AM this morning with wind gusts to 38 MPH. Nothing more than what a stronger summer thunderstorm would provide. I looked at several observation sites and .03″ was the most I could find between 7 PM last night and 1 AM Tuesday morning. They waited until 30 minutes before game time to cancel. By that time all the information I posted in my previous comment was and had been available for several hours and any radar was only showing one small band that was going to move through between 8:30 and 9:30 PM. Obviously other showers could have developed but the severe chance had been downgraded by this time. Not sure why they decided to postpone other than they (i.e. MLB) believed there was still a safety risk. Atlanta would postpone a lot of games if they would go by the similar conditions of possible heavy rain and isolated severe storms.

***Weather Summary *** Metman Weather Services 22 Jul 2019 9:05 PM EDT Washington DC (postponement of Nats game)
MLB postpones Nats game based on forecast not actual weather occurring:

No rain yet today and no rain anticipated until isolated/scattered showers and storms developing by about 8:30 – 9:00 PM tonight ( a brief shower is now occurring). The line of severe storms, if at all (see below) won’t be until after midnight, maybe significantly after midnight. Current radar confirms this. Someone took a picture at 7:45 of partly cloudy skies and the sun shining. Most models I reviewed are showing very little rainfall for the time period. The NAM and high resolution models along with other models are in agreement for .1-.2″ or less through 11 PM. Only the Canadian model has any significant accumulation. Pretty sure they could have played at least 5-6 innings and maybe even got the whole game in, albeit they may have had a short delay. I’m all for safety first but unless this game ran over 4-5 hours no severe weather was expected (see below) during the game time and later and even then the chances were negligible to low per the 18Z model runs and hourly high resolution models. Many fans are now complaining they made the trip and can’t go to a 1 PM game Wednesday due to other commitments. Numerous showers and low possibility of severe storms are set to overrun the area after midnight, maybe well after midnight, but they had a window to play and chose to cancel.

Forecasted severe weather parameters (NAM and HRRR) for 8 PM
Mid level CAPE(350 -450 j/kg) Weak
Surfaced Based CAPE (780 -1300 j/kg) Weak to Moderate
Lifted Index (-3 to -5) Moderate
SR Helicity 0-3Km (45-100) Low
Energy Helicity 0-3Km (.4) Low (>1 for supercell or tornado)
SigTor Negligible
Bulk Shear Low
Mid Level Lapse rate 5.6 Moderate (over 6 is High)

Isolated/scattered strong storms possible with some damaging winds possible but chances of anything more severe and tornados was low.

Note: These are general mesoscale indices and are to be used as a guide. A low probability doesn’t necessarily mean no chance as other factors must be considered and weighted when using these indicators. In this case I didn’t’ find any other factors to alter the guidance. Also, microscale anomalies are always a possibility as mesoscale indicators don’t necessary account for possibilities on a smaller scale thus you can completely rule out severe weather if indices are low as they could be somewhat higher in isolated microscale locations.

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***Weather Update*** METMAN WEATHER SERVICES 4:15 EDT 20 Jul 2019 BRAVES GAME FORECAST

Probably won’t be around for the start of the game so here’s a short note.

Models are fairly consistent that only .1-2 or less for the game time frame. A shower or storm is possible this evening and most of the vicinity in the early time period. Th HRRR high resolution model is, however, showing a bit stronger chance for some isolated strong areas of showers and storms in the vicinity (especially SE/S moving E/NE) for most of the game time period. Abundant moisture in the atmosphere but cloud cover in N GA has limited convective development so far through the area. Chance for severe weather are low but an isolated severe storm is possible. Storm movement will be generally be slow so .5-1″ or more in a few areas is possible. I generally think we’ll be OK and I’ll check the radar when I get back. Sorry I didn’t have a little more time to delve into the specifics.

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***Weather Forecast Update*** METMAN WEATHER SERVICES Thursday 25 APR 2019 4:45 PM EDT Cincinnati, OH (Braves game)

Shower and a few thunderstorms around tonight should be a little more formidable than last night but still mostly light with occasional moderate to possibly some brief heavier showers mixed in at times. Most of the heavier rain should stay just to the north and west but some brief moderate to heavy downpours can’t be ruled out from the 7-10 PM time period. Models, except the 18Z NAM which generates slightly heavier precipitation but has come down considerably since the 12Z run, are generally in agreement for .25″ or less through 10 PM although the high resolution models are beginning to trend upward with rainfall totals (.15″ to .35″ RAP and .1″ to .25″ HRRR over the previous hourly run). I usually trust HRRR a little more this close to an event (it seems to model convective development a bit better). CIN (convective inhibition) is low but instability is marginal based on CAPE (Convective Available Potential Energy). In any case, it looks like a little soggy evening and possibly a delay or two if a moderate shower lasts long enough or a brief heavy shower/thunderstorm were to occur but they should be able to get the game in unless the upward trend of rainfall totals continues, a real but still questionable possibility at this time. I’ll check the radar as we get closer to game time.

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2/20/2019
Certainly there will be upper level divergence and enhanced vertical motion along with baroclinicity. I was concerned that conditions conducive to conditional symmetric instability (CSI), i.e. EPV/theta-e overlay, or also known as a type of moist slantwise convection, during upper level frontogensis will provide banding and enhance snowfall amounts through the morning and early afternoon hours. It appears that may be happening or has happened but I don’t have the tools necessary to analyze that type of situation. Perhaps I am overusing CSI, which occurs frequently, as a reason for heavier snow but it appears that atmospheric profiles make it more of a possibility in this event. I could even see a possibility of convective instability (CI) overriding CSI and triggering thunder snow in a few spots. That might be a be a push. Snowfall will probably only be about 5-7 hours and it certainly could fall very heavily during those times. Marginal thermal profiles aloft and delay in the warm advection could push back the transition to mixed precipitation for several hours adding several inches to the totals.

Conditional Symmetric Instability…
https://journals.ametsoc.org/view/journals/wefo/13/1/1520-0434_1998_013_0084_eaaocs_2_0_co_2.xml?rskey=eYdlyK&result=9External Link
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*** WEATHER Discussion*** METMAN WEATHER SERVICES 19 Feb 2019 9:05 AM Harrisburg, PA

Certainly there will be upper level divergence and enhanced vertical motion along with baroclinicity. I was concerned that conditions conducive to conditional symmetric instability (CSI), i.e. EPV/theta-e overlay, or also known as moist slantwise convection, during upper level frontogensis will provide banding and enhance snowfall amounts through the morning and early afternoon hours. It appears that may be happening or has happened but I don’t have the tools necessary to analyze that type of situation. Perhaps I am overusing CSI, which occurs frequently, as a reason for heavier snow but it appears that atmospheric profiles make it more of a possibility in this event. I could even see a possibility of convective instability (CI) overriding CSI and triggering thunder snow in a few spots. That might be a be a push. Snowfall will probably only be about 5-7 hours and it certainly could fall very heavily during those times. Marginal thermal profiles aloft and delay in the warm advection could push back the transition to mixed precipitation for several hours adding several inches to the totals.

2.75″ in Enola as of 11 AM.

P.S. I thought a general area total of 3-6″, more to the W and SW.

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When you think of all the things that were right there is really little to complain about.

1. Forecast the storm from 4-7 days out while the energy was still in the Pacific Ocean.
2. Forecast the time frame early Saturday PM to early Sunday PM at least 3-5 days in advance.
3. Forecast the snow, mixed, and possibly rain scenario and general timing of those events 3-4 days in advance.
4. Forecast the arrival of the storm with several hour if not exact timing 4 days in advance.
5. Forecast the changeover from snow to mixed precipitation in a two hour window virtually exactly on time 4 days in advance.
6. Forecast the changeover to rain overnight almost exactly 4 days in advance.
7. Forecast surface temperatures in the low 30 to mid 30’s and rising to the mid to upper 30‘s overnight 4 days in advance even though it didn’t agree with model guidance at that time .
8. Forecast warm air advection aloft up to 5K ft to move in Saturday evening and remain overnight for an 8-12 hour period creating a snow to mixing to rain scenario.
9. Forecast 3-5″ of snow Saturday afternoon and early evening before mixed precipitation begins.
10. Forecast more snow north and less south with areas to the S receiving only a coating to 2″.
11. Forecast the total liquid equivalent (1.5″± .25″) with within .1” of the exact amount. (1.6” per HBG hourly observations).
12. Forecast the bottom 1/3 of the forecast area with precision 4 days in advance.
13. Forecast possible snow after the cold air moved in. (We’ve had flurries and radar currently showing light snow in the area).
14. Issued forecast updates and update accumulation totals expected before and as the storm played out citing track of low and somewhat less snow, mix (and ice) and more rain.
15. Forecast extremely cold air and high winds with sharply falling temperatures moving in after the storm Sunday and Sunday night with single digits by Monday morning 4 days in advance. (not a check yet but pretty confident it’s now happening).
16. Just verified-Forecast low temperature in the mid single digits Monday morning nearly 6 days in advance. (7°F per HGB hourly observations)

All of these were posted FOUR days or more in advance of the storm!

Finally, snow totals come in 2-3” below initial the forecast but in many areas accumulation totals will still verify in the lower half of the forecast range and we’re not believable, worthless, overpaid, and wrong 90% of the time weather guessers.

These quotes about perception say it all…
“Facts matter not at all. Perception is everything. It’s certainty.” Stephen Colbert
“There are things known and there are things unknown, and in between are the doors of perception.” Aldous Huxley

Metman Weather Services Forecast
In Storm Update 8:45 PM EST Saturday 19 Jan 2019 Harrisburg, PA

It appears that the warm air is winning out, which if you’ve followed my narrative was a distinct possibility. The low pressure system is SW of the area and taking a more northerly track this evening putting us on the milder side of the storm with slightly warmer temps at the surface and aloft, less snow and more rain throughout the entire forecast region. It is expected to move easterly track overnight before turning to the NE into New England tomorrow. Temps at the surface are still in the mid 30’s. Temps should remain steady or rise several degrees overnight but it’s looking more like the advection aloft (surface-5K ft) along with the warmers temperatures at the surface is going to somewhat mitigate the snow accumulation for this storm in the I81/I78/ turnpike corridor and areas farther north, although it’s possible that accumulations may reach the bottom or even middle of the forecasted ranges. QPF’s (~1.5″) will wind up being mostly in rain for the lower two thirds of the forecasted area and about 1/2 in the upper forecast area. In many instances snow will be be somewhat under-performing expected accumulations, especially in the northern 2/3 of the forecast area, and will be closer to the bottom of the ranges issued in the final storm update earlier today and maybe below those ranges in some areas but I wouldn’t rule out some heavier snowfall rates before the changeover occurs that bring accumulation well within the previously forecasted range.

Most accumulation totals and point forecasts in the upper two thirds of the forecast area will be less but should fall at the bottom of the range or just below the previously forecasted range posted here…
(https://www.pennlive.com/news/2019/01/heres-how-much-snow-forecasters-expect-this-weekend.htmlExternal Link).
These forecasts with surface temperatures hovering around freezing or just above in combination with warm air advection aloft and other mesoscale dynamics with evolving synoptic scale winter systems makes it a very difficult forecast.

Summary:
The lower third of the forecast area requires little change:
Includes Chambersburg, York, and Lancaster
Snow at first, then mixing, then rain. Mostly rain in most areas. Possibly ending with coating of snow in some areas.
Snowfall of C-2″, locally higher in spots, more to the NW and less to the SE
QPF accumulation percentage: :10%-20% snow and mix, 80-90% rain
Little to no accumulation changes in eastern areas, accumulation 2-3″ lower in western areas

The middle third of the forecast area:
Includes Carlisle, Harrisburg, Dauphin, Hershey, Elizabethtown, and Reading, Turnpike. most of I81
Snow at first, then mixing, then rain. More rain and mix than snow. Possibly ending with C-1″ snow in some areas.
Snowfall accumulation of 2-5″, locally higher in spots especially in higher elevations, more to the NW and less to the SE
QPF accumulation percentage: ~25-30% snow and mix, ~70-75% rain
These amounts represent 2-3″ reduction in accumulation for this area

The upper third of the forecast area:
Includes Duncannon, Millerstown, New Bloomfield, Halifax, Millersburg, Carsonville, Lykens
Snowfall accumulation of 4-8″, locally higher in spots especially in higher elevations, more to the NW and less to the SE
Snow at first, then mixing, then rain. More rain and mix than snow. Possibly ending with C-1″ snow in some areas.
QPF accumulation percentage: 40-60% snow and mix, 40-60% rain
These amounts represent 2-3″ reduction in accumulation for this area

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Metman Weather Services Forecast
Final Update 10:30 AM EST Saturday 19 Jan 2019 Harrisburg, PA

Event still looks like Saturday afternoon thru early Sunday afternoon. Models are becoming more congruent if not exactly similar. The NAM (North American Model) has come into agreement with the majority of models. Th last model runs are trending wetter not whiter favoring more warm air aloft, more rain, and less mixing once the transition begins Saturday evening. My forecast uses a unique blend of models (global, regional, ensembles) modified to specific synoptic analysis to current conditions with local adjustments by mesoscale analysis of various parameters such as omega (vertical velocity), shear, moisture and saturation, thermal profile, DGZ (Dendritic Griwth Zone), thickness, vorticity etc. as determined by atmospheric profiles. For this event, at least initially, the bias seemed to be for slightly heavier snow amounts than what actually occurred.

Precipitation will start out as light snow or a mix early Saturday afternoon, then snow turning heavier later in the afternoon and evening and then transitioning to mixed precipitation (snow, sleet, and freezing rain) later Saturday evening evening between 7 PM and 10 PM (I’m expecting an 8-12 hour period of mixed precipitation, 4-10 hours could fall as mainly rain ) as temps at the surface remain steady or rise slowly possibly into the mid 30’s in the Harrisburg area. Temperatures at lower levels aloft (850 MB, ~5K ft) and 925 MB, ~2.5K ft) will rise for a 6-12 hour period creating mixed precipitation and rain during that period before the arctic air begins to sweep in Sunday morning. If the temperatures in the lower layer from the surface to 925 MB (approx 2.5K ft) rise above freezing as the transition is taking place the change from snow to mix to rain could happen quickly (less than 3 hours) and limit the accumulation of sleet hindering a accumulations later Saturday and into Sunday morning. This is a possibility for some areas adjacent to and north of the turnpike and may result in accumulations being in the lower half or possibly even below the forecast range in those areas.

For the immediate Harrisburg area, expect 3-5″ of snow Saturday afternoon and evening before mixed precipitation starts, then mixed precipitation turning to rain later Saturday evening and early Sunday morning and then another C-1″ of snow Sunday. Up to .25″ or more of ice is also possible Saturday night into Sunday morning. Mean QPF’s (Quantitative Precipitation Forecast) remain about 1.5″± .25″ and expect ~1/2 of that, more or less depending on location and other factors, to fall as mixed or even mostly liquid precipitation in areas farther to the S&E.

Higher accumulations for the immediate Harrisburg area will be mitigated by mixing and rain Saturday night and Sunday morning but expect 4-8″ of totaled measured accumulation (snow/sleet) for the event including a possible C-1″ later Sunday AM and early PM when things get colder after the arctic air begins to entrench itself. Areas farther to the north that are E and W of Harrisburg (i.e. Perry, Juniata, central and northern Dauphin) and elevated localities could get 8-12″+ accumulations if the warm air aloft only extends for a short duration, otherwise, expect 5-10″ with locally higher amount possible. Areas S & SE of Harrisburg can expect 3-6″, and areas father to the S and SE (southern portions of York and Lancaster counties) where the precipitation is mostly mixed and more rain, especially near the PA/MD border can expect just a C-3″ as they will have a longer period of liquid precipitation than areas farther north.

Areas to the west and south of Harrisburg along I81 near Chambersburg can expect 4-6″, with locally higher amounts possible, and areas farther south adjacent to and west of I81 can expect 2-4″. I81/78 from Chambersburg into Berks County seems to be a good line between the more accumulating snow (5-6″ or more north and west and less than 6″ south and east) and more mixed precipitation and rain to the south and east but anomalies will exist with this demarcation and it’s possible that this line could move considerably, especially north if the warm air advection at the lower levels (surface to 5K ft) moves in earlier rather than later creating a longer duration and the warm layer is deep resulting in more liquid precipitation.

Temperatures should start falling sometime Sunday morning and the winds will become much stronger at 15-25 MPH with higher gusts to 40+ MPH out of the NW. Temperatures will plummet about 30°F or more Sunday from highs in the mid 30’s or higher Sunday morning to the mid single digits by Monday morning with the arrival of the arctic air. This will create flash freezing condition later Sunday morning.

Summary:
I didn’t have time to do another complete analysis but current indications are that temperatures in the lower level may warm enough to keep mixing, especially sleet, to a minimum (less than 3 hours) and promote a quicker transition to rain even farther into northern areas, especially in Perry, Dauphin, and Lebanon. This is a very difficult forecast for the mid and northern regions of the forecast area, including the I81/I78/turnpike corridor and areas to the north, where accumulations, mostly downwards, may vary greatly within a narrow gradient. If this occurs it could limit accumulations needed to reach the point forecast amounts below.This would result in accumulations at the bottom or even below the forecast range in many areas.

County and City Point Forecast:
Note: Confidence is medium to high except for areas adjacent to and north of the I81/I78/turnpike corridor from Chambersburg to Berks County where confidence is medium due to mixing and uncertainty and transition to just rain. Please refer to the county range in these areas.

Adams 3-6″ north, 2-4″ south
Gettysburg 4″
Berks 3-6″
Reading 4″
Cumberland 4-6″, locally higher possible
Carlisle 6″
Enola 6″
Lisburn 4″
Mechanicsburg 5″
Shippensburg 5″
Dauphin 5-10″ north, locally higher possible, central 4-8″ south,
Halifax 8″
Harrisburg 5″
Hershey 5″
Middletown 5″
Millersburg 8″
Franklin 2-6″
Chambersburg 5″
Waynesboro 2″
Lancaster 2-5″ north, C-3″ south
Elizabethtown 4″
Lancaster 2″
Lebanon 4-8″ north, 2-6″ south
Lebanon 4″
Perry 5-10″ north, higher locally possible, 4-8″ south
Duncannon 7″
Millerstown 9″
New Bloomfield 7″
York 2-5″ north, C-3″ south
Dillsburg 4″
Hanover 1″
York 2″

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Metman Weather Services Forecast Update 7:15 PM EST Thursday 17 Jan 2019 Harrisburg, PA

First event…
Thursday evening until Friday morning. QPF’s are < .1-.2″ over the area. Temps at the surface and aloft should be cold enough to support all snow. A general C-2″ over the south central PA area. A few places could get up to 3″, especially in the higher elevations. It appears the chances for any mixed precipitation will stay to the south of the PA border as temperatures aloft and at the surface should remain below 32°F through the duration of the event. I wouldn’t rule out a very brief period of mixing in some isolated areas near the PA/MD border as the event ends.

Second event…
Currently looks like Saturday afternoon thru early Sunday afternoon. Models are starting to come into agreement. The Euro with its slower movement, colder temps aloft , and excessive snowfall is coming back to the pack now. At this time the NAM is now the outlier and has pushed any significant snowfall to the N and W.

Second event…
Currently looks like Saturday afternoon thru early Sunday afternoon. Models are starting to come into agreement. The Euro with its slower movement, colder temps aloft , and excessive snowfall is coming back to the pack now. At this time the NAM is now the outlier and has pushed any significant snowfall to the N and W.

Precipitation will start out as light snow or a mix Saturday afternoon, then snow turning heavier in the evening and then transitioning to mixed precipitation (snow, sleet and freezing rain) later Saturday evening or early Sunday morning between 8 PM and 2 AM (I’m expecting a 6-12 hour period of mixed precipitation) as temps at the surface remain steady or rise slowly to around 32°F. Temperatures at lower levels aloft (850 MB, ~5K ft) will rise for a 6-12 hour period creating mixed precipitation during that period before the arctic air begins to sweep in Sunday morning. Some models have temps getting into the 40’s near Harrisburg and higher S&E. I’m currently going with low 30’s and possibly mid 30’s for very early Sunday morning (40°F or even low 40’s maybe briefly in areas farther S&E of HBG) before temps turn sharply colder and winds pick up.

For the Harrisburg area, expect 3-6″ Saturday afternoon and evening before mixed precipitation starts, then mixed precipitation overnight and then another C-2″ of snow Sunday. Up to .25″ or more of ice is also possible Saturday night into Sunday morning. Mean QPF’s are about 1.5″± .25″ and expect ~1/2 of that, more or less depending on location and other factors, to fall as mixed or even liquid precipitation in areas farther to the S&E.

Total accumulation for the Harrisburg area will be mitigated by mixing later Saturday night and Sunday morning but at this time expect 4-8″ (isolated up to 10″) of totaled measured accumulation for the event with another C-1″ possible later Sunday AM and early PM when things get colder after the arctic air begins to entrench itself. Areas farther to the north that are E and W of Harrisburg (i.e. Perry, Juniata, central and northern Dauphin) and elevated localities could get 6-12″. Areas S & SE of the Harrisburg vicinity (outside a 15 mile radius) can expect 3-6″ (isolated up top 8″), areas father south and to the SE where the precipitation is mostly mixed with rain or mostly rain in some spots, especially near the PA/MD border can expect just a C-3″ as they will have a longer period of liquid precipitation than areas farther north.

New for Sat forecast: Total accumulation for the Harrisburg area will be mitigated by mixing and maybe just some rain for a while later Saturday night and Sunday morning but at this time expect 4-8″ and possible of totaled measured accumulation for the event with another C-1″ possible later Sunday AM and early PM when things get colder after the arctic air begins to entrench itself. Areas farther to the north that are E and W of Harrisburg (i.e. Perry, Juniata, central and northern Dauphin) and elevated localities could get 5-10″ and possibly more if the warm air aloft does not extend that far north or only extends for a short duration. Areas S & SE of the South of Harrisburg (generally south and east of I81/I78 and north of route 30 and areas west of Route 15 and north of Route 30) can expect 3-6″, areas father south and to the SE where the precipitation is mostly mixed with rain or mostly rain in some spots, especially near the PA/MD border can expect just a C-3″ as they will have a longer period of liquid precipitation than areas farther north. Areas south of route 30 and east of York can expect C’-3″ due to mostly mixing and even just plain rain. Areas south of route 30 and west of York can expect 2-4″.

Areas to the west and south of Harrisburg along I81 south to Chambersburg can expect 4-8″ and areas farther south along and west of I81 can expect 3-6″. I81/78 seems to be a good line between the more accumulating snow and more mixed precipitation.

County/City forecast quick reference:
Adams 3-6″ north, 2-4″ south
Berks 3-6″
Reading 4″
Cumberland 4-8″
Carlisle 6″
Enola 6″
Dauphin 5-10″ north, 4-8″ central, 3-6″ south
Harrisburg 5″
Franklin 4-8″ north, 2-6″ south
Chambersburg 5″
Shippenburg 6″
Waynesboro 4″
Lancaster 2-5″ north, C-3″ south
Lancaster 3″
Lebanon 6-8″ north, 4-6″ south
Lebanon 6″
Perry 5-10″ south, 8-12″ north
Duncannon 7″
New Bloomfiled 8″
York 3″

Temperatures should start falling sometime Sunday morning and the winds will become much stronger at 15-25 MPH with higher gusts to 40+ MPH out of the NW. Temperatures will plummet about 30°F or more Sunday from highs in the mid 30’s or higher Sunday morning to the mid single digits by Monday morning with the arrival of the arctic air. A final update Saturday morning.

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Metman Weather Services 2:45 PM EST 15 Jan 2019
My way to early weekend forecast first look:

Two events later this week.
First event…
Thursday evening until Friday morning. QPF’s are .1-.3″ over the area. Temps at the surface and aloft should be cold enough to support mostly all snow.This one is pretty much agreed upon with generally 1-3″. The only caveat I would add is that if warm air aloft (and maybe even down to the surface in southern areas) advects into the area before the precipitation ends there could be a period of freezing rain/freezing drizzle or mixed precipitation or even plain rain early Friday morning, especially in the southern areas of Adams, York, and Lancaster counties. Now I’m going to skip to the biggie this weekend.

Second event…
Currently looks like Saturday afternoon thru early Sunday afternoon. Precipitation will start out as light snow Saturday afternoon then transition to mixed precipitation later Saturday evening (~8-10 PM) then to mostly rain overnight (I’m expecting at least a 4-6 hour period of mainly rain but this could change to a mixed precipitation) as temps at the surface and aloft to rise for an 8-12 hour period before the arctic air sweeps in Sunday morning. Some models have temp getting into the 40’s and even near 50. I think it’ll be a little hard to get that high so I’m currently going with mid 30’s and possibly upper 30’s for very early Sunday morning before temps turn sharply colder and winds pick up. Expect 3-5″ Saturday afternoon and evening before mixed precipitation/rain starts, then about .5-1″ of liquid precipitation and then another C-2″ of snow later Sunday AM and early Sunday PM. Up to .1″ of ice is also possible Saturday night into Sunday morning. Mean QPF’s are about 1.5″ and expect 1/2 of that, more or less depending on location and other factors, to fall as liquid precipitation. Total accumulation will be mitigated by mixing/rain but at this time I’m thinking 3-6″ or possibly 4-8″ (depending on timing, location, track, and type of precipitation) of measured accumulation before another C-2″ is possible later Sunday AM and early PM when things get colder after the arctic air begins to entrench itself.
Generally more snow to the N and less to the S. Places near the PA/MD border may only accumulate a coating to 2″ as they will have a longer period of liquid precipitation than areas farther north. Temperatures should start falling sometime Sunday morning and the winds will become much stronger at 15-20 MPH with higher gusts out of the NW. Temperatures will plummet about 30°F or more Sunday from highs in the mid 30’s or higher Sunday morning to the mid single digits by Monday morning with the arrival of the arctic air. The exact timing and precipitation amounts and expected temperatures of the events may change somewhat as new data comes in but this is a general summary as of today. Small changes in atmospheric profiles and a few degrees colder than the current expected surface temperatures could mean more mixed frozen precipitation Saturday evening and Sunday morning and less liquid precipitation resulting in higher accumulations. Very tough forecast but things should clear up as we get closer to Saturday but even then a swing of a few degrees in temperatures at the surface or aloft could make forecasting these amounts very difficult.
Note that this forecast is for the Harrisburg area. Areas more than a 30 mile radius may experience somewhat different results, especially to the south where the warm air aloft and at the surface will arrive first and leave last thus creating less accumulation of snow and longer periods of mixing and especially rain, which will significantly reduce snowfall accumulations in those areas.

Welcome to winter!

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Hurricane Florence Sep 2018

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

Hurricane Florence Monitored Sep 7 – Sep 17 2018 (first Forecast at bottom moving up to to the last update)

weathertrends360
“Hurricane Florence has set the record by far for the wettest Tropical System in North Carolina history, breaking Floyd’s 1999 record of 24.06”.
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Sep 17, 2018 at 10:57 AM
Remnants of Florence started moving into my area in south central PA around 10 AM this morning. Rain today, tonight and through tomorrow afternoon is expected generally totaling about 1.5″, more to the mountains just to the east and north.

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Just a quick question…

So when this was a higher category storm and the predictions were a bit more dire, weren’t things like shallow water providing less energy and land friction expected and wouldn’t that have led to predictions that the storm would weaken as it has? Genuine curiosity as I have always been curious about these things. When I was at university, one of my professors in physical geography tried to steer my education in that direction that included meteorology.”

Yes they were and are in every instance. I mentioned them as factors because they were expected to decrease intensity somewhat over time but aided by the lack of intensification after the uncompleted ERC also. Perhaps I should have emphasized the ERC more. In this case the eyewall replacement cycle (ERC) never completed. The eastern portion never filled in and the lack of a complete eyewall destroyed the structure of the hurricane needed for intensification. Florence later developed what is know as concentric eyewalls (an inner stronger wall and and outer weaker wall), a condition that is unfavorable for intensification when intensification was expected to increase under favorable conditions. That condition is probably a big reason for the decrease in intensity and is not unusual but is nearly impossible to forecast. If I remember correctly Hurricane Matthew had a similar occurrence. Like I said, sometimes hurricanes are just a different animal. In addition, the whole system got much larger area wise after the uncompleted ERC, a normal occurrence with an ERC, and the energy became more widespread out over a larger area. This is normally overcome by a stronger core (i.e. one eyewall with stronger winds) after ERC completion and intensification if conditions are favorable, which they were, only in this case the structure of the eye was not conducive to intensification. Add in the slower movement over shallower water providing less latent heat due to upwelling colder water and the other usual factors affecting intensification and you get a significant drop in strength.

Sorry for the long length of the reply. Hope this helps!

Note: I should also add that although I have a general and specialized education on tropical systems, including tropical cyclones and their causes and effects. My experience with tropical systems is mostly theoretical and lab related exercises on past hurricanes and their movement, structure, development and characteristics. I do not have an in depth working knowledge and extensive application of tropical meteorology including forecasting tropical cyclones nor do I claim to be an expert on tropical and subtropical systems, cold core/warm core systems nor developing systems in either a barotropic or baroclinic atmosphere. On the contrary, my expertise lies more with research in desert and cold weather/arctic atmospheric profiling, middle and upper atmospheric research, and microscale, mesoscale, and synoptic scale operational and weather environmental forecasting.

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***Florence Update*** METMAN WEATHER SERVICES Thursday Sep 13 2018 11:10 AM EDT

Here is an excerpt from my synopsis this morning. Maybe this will shed a light to why Florence is not as strong.
Florence is expected to slow and veer more to the west as she nears the coast. Several factors will reduce the expected intensity from yesterday and will take its toll on Florence and reduce its intensity by a full category.

1. Slower movement over shallow water
2. Shallow water providing less energy
3. Land friction as it nears the coast
4. Increased atmospheric wind shear

Although Florence is moving into atmospheric conditions that are favorable for intensification these will be mitigated greatly by the above mentioned factors causing a net loss of strength as Florence nears landfall. The eye wall has never fully developed after the ERC yesterday and there are low clouds in the eye and the overall hurricane is less symmetrical and as a result the maximum winds are less and the energy is more spread out. This will definitely reduce the wind damage that would have been caused by a CAT 3 or CAT 4 hurricane. Florence is expected to make landfall Friday morning around 5 AM plus or minus 6 hours. This could change slightly, possibly later Friday, depending on the accuracy of the forecasted slower movement. Maximum sustained winds at impact are expected to be 90-110 MPH. That’s a high CAT 1 to a high CAT 2. Winds will likely remain a CAT 2 through most of Friday then a CAT 1 before being downgraded to a tropical storm on Saturday. If it should stall just off the coast it could remain a CAT 2 until Saturday and them remain a low CAT 1 for a day or two before reaching tropical storm status but that’s much less likely. The path I delineated in my previous update is still pretty much on target with all the newest model runs except it may veer a little more east as it travels northward early next week. This is still a very dangerous storm that will cause significant wind damage, heavy rainfall, torrential flooding, and dangerous storm surges. Expect rainfall amounts from 15-30″+ east of I95 from the central SC to central NC coast and 5-15″ in SC, especially central and eastern SC and central and southern NC. Other areas in SC and NC can expect .5-5″, more where orographic lift enhances precipitation. Inland areas such as eastern and central GA, eastern TN, eastern KY, southern VA, WV and into the lower mid Atlantic states next week can also expect .5-5″, more where orographic lift enhances the precipitation. Please heed any and all weather warnings, flood warnings, and hurricane warnings and keep in contact with local emergency authorities if you live in any of these areas, especially in the Carolinas, as devastating winds, torrential rainfall, high storm surges, and catastrophic flooding are imminent!

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***Florence Update*** METMAN WEATHER SERVICES Wednesday Sep 12 2018 10:30 AM EDT
Just a quick update. Most models are now sinking the path to the south and support stalling within 50 miles of the coast or just inland for up to several days. The flow aloft around the high pressure area driving the storm to the west will break down leaving Florence with no steering current. This is becoming more of a reality than a possibility. This could bring catastrophic rains and flooding from coastal southern NC (24-36″+) into southern coastal SC (12-15″). Areas in coastal SC and coastal GA from Brunswick north are now possibly in play for heavy rains and flooding if Florence were to drift far enough to the south and come ashore between Savannah and Charleston, SC. Still a lot to be determined.

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“I noticed on a local map they had now extended the most southern zone as far down as Athens Ga with an inland track then curving up
through NE Georgia.That’s just the outer-most area though so I imagine that means just some good rain and moderate winds.”

Absolutely a possibility when you look at the European model. Even a few other models have if falling apart and moving through SC and GA. As it moves west the interaction with the mountains will decrease the strength rapidly but 2-6″ or more of rain in the northern GA is not out of the question in this scenario, the heaviest amounts falling to the east of the metro area with the orographic lift in higher terrain. Also, the 18Z GFS run is aligning with the Euro model in the scenario I mentioned in the last post although that model brings it inland to central SC and then turns north into western NC. In that scenario northern GA is mostly spared the heavy rainfall (only about .25″-2″). My gut feeling at this time is that about 1″ of rain will fall in north central GA between Saturday and Monday although a slight shift to the north earlier would result in less than 1″ or possibly even less than .5″ total on those days. A shift to the west would likely result in 1-3″ for northern central GA.

In addition, the timing of landfall, if in fact it does make landfall in NC, keeps moving back slightly with each model run and also impacts regions farther to the south into southern SC. The North American Model (NAM), a regional model, has the storm meandering off the coast from late Thursday evening until finally making landfall in southern NC early Saturday morning. Dry air aloft and an expected increase in wind shear on Thursday in addition to moving slowly over shallower waters providing less latent heat energy will probably result in a CAT 3 hurricane or minimal CAT 4 (if you can call a CAT 4 minimal anything). Other scenarios have the storm making landfall early Friday morning between Myrtle Beach, SC and Nags Head NC. At the present time pending new data input from reconnaissance missions and other data gathering sources, I think a good compromise weighing model reliability and other factors would have the storm just off the coast or slightly inland in southern NC around Wilmington, NC on Friday morning and then meandering slowly just off the coast and drifting slowly south for at least 12-24 hours before continuing west through northern SC then turning north through western NC, eastern TN, eastern KY then moving into Indiana/Ohio.

I’m still somewhat apprehensive of a southern SC landfall and more westerly track afterwards but it’s hard to discredit two major dynamical models, although not coupled with ocean models, that are displaying congruent but not identical output, especially when the updated physics of the GFS V3 model drives the hurricane farther south like the Euro model also. I do therefore consider that southerly movement and drifting into my prognosis. Most other models, including coupled ocean models like the GDFL and HWRF and others featured in the spaghetti plot, are consistent with the southern NC landfall scenarios early Friday morning and the westerly/northwesterly track afterwards. That’s the way I see it currently. Still much can change from now until landfall and after it makes landfall. Now that I’ve said all of that any new data input into future model runs could change that scenario somewhat or even a lot, especially after the initial landfall or the close to landfall situation in southern NC Friday morning.

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***Florence Update*** METMAN WEATHER SERVICES Tuesday Sep 11 2018 9:00 PM EDT

Absolutely a possibility when you look at the European model. Even a few other models have if falling apart and moving through SC and GA. As it moves west the interaction with the mountains will decrease the strength rapidly but 2-6″ or more of rain in the northern GA is not out of the question in this scenario, the heaviest amounts falling to the east of the metro area. Also, the 18Z GFS run is aligning with the Euro model in the scenario I mentioned in the last post although that model brings it inland to central SC and then turns north into western NC. In that scenario northern GA is mostly spared the heavy rainfall (only about .25″-2″). My gut feeling at this time is that about 1″ of rain will fall in north central GA between Saturday and Monday although a slight shift to the north earlier would result in less than 1″ or possibly even less than .5″ total on those days. A shift to the west would likely result in 1-3″ for norther central GA.

The timing of landfall, if in fact it does make landfall in NC, keeps moving back slightly with each model run and also impacts regions farther to the south into southern SC. The North American Model (NAM), a regional model, has the storm meandering off the coast from late Thursday evening until finally making landfall in southern NC early Saturday morning. Dry air aloft and an expected increase in wind shear on Thursday in addition to moving slowly over shallower waters providing less latent heat energy will probably result in a CAT 3 or maybe a very minimal Cat 4 hurricane (if you can call a hurricane of that force minimal anything). Other scenarios have the storm making landfall Friday morning between Myrtle Beach, SC and Nags Head NC. At the present time pending new data input from reconnaissance missions and other data gathering sources, I think a good compromise weighing model reliability and other factors would have the storm just off the coast or slightly inland in southern NC on Friday morning and then meandering slowly just off the coast and drifting slowly south for 12-24 hours before continuing west through northern SC then turning north through western NC, eastern TN, eastern KY then moving into Ohio/western PA.
I’m still somewhat apprehensive of that scenario but it’s hard to discredit two major dynamical models, although not coupled with ocean models, that are displaying congruent but not identical output, especially when the updated physics of the GFS V3 model drives the hurricane farther south also like the Euro model. Most other models, including coupled ocean models like the GDFL and HWRF and others featured in the spaghetti plot, are consistent with the southern NC landfall scenarios and the westerly/northwesterly track afterwards.. That’s the way I see it currently. Still much can change from now until landfall and after it makes landfall. Now that I’ve said all of that any new data input into future model runs could change that scenario somewhat or even a lot, especially after the initial landfall or the close to landfall situation in southern NC early Friday.

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***Florence Update*** METMAN WEATHER SERVICES Tuesday Sep 11, 2018 10:30 AM EDT

Just a quick note to all. There is very good agreement in all models for this storm and it has the potential to be CATASTROPHIC! Landfall looks to be very late Thursday night to possibly dawn on Friday morning. This will be a very slow moving storm that will most likely hover for several days on or near the coast or just inland (inland would be significantly better) before finally moving inland and eventually slowly dissipating. Expect very heavy rain, catastrophic flooding, high storm surges and plenty of severe weather along the North Carolina Coast and the inland areas in North Carolina, especially areas near and east of I95, but also the southern Virginia and South Carolina coast, before slowly dissipating. The track is currently for the storm to strike in southern North Carolina between the North Carolina/South Carolina border and Morehead City, NC. At the current time, the Wilmington to Jacksonville, NC area seems to be the target. This path could change slightly over the next several days but at this time is not expected to go any farther south than Myrtle Beach, SC nor farther north than Nags Head, NC. Remember, the heaviest precipitation and most severe weather will be near and just to the north of the eye and could extend for several hundred miles. This storm has the potential to deliver up to 3-4 feet of rain in some locations on the North Carolina coast and the situation could resemble what Harvey did to Houston last year. Once the storm moves inland Sunday or early next week it could track as far south as into South Carolina then into Georgia or take a track more westerly through North Carolina. This is a very dangerous storm. Anyone in the coastal impact areas near the South Carolina, North Carolina or southern Virginia/Maryland coastal areas should heed all warnings immediately and prepare to evacuate or move to higher ground. I REPEAT…THIS IS A DANGEROUS LIFE THREATENING STORM!! PREPARE AND ACT NOW IF YOU LIVE IN ANY OF THE AREAS I MENTIONED, especially if you live on or within 50 miles of any of these coastal areas! Please keep in contact with your local authorities, emergency organizations, and heed any weather warnings related to this hurricane.

Latest update on Florence from weathertrends360
1:30 PM EDT Sep 10, 2018 Monday Captain’s Log & video update on Major Hurricane Florence.
North Carolina area from Wilmington to Morehead City most likely to take a direct hit Thursday into predawn Friday with a Cat 4 per NHC (sustained 150 mph gusting to 184 mph)!
Be safe folks and remember a storm surge of 10-15 feet (right of the eye) is simply the ocean rising up, a wall of water…on top of that are 20-30 foot waves so the net is 30-40 foot seas to the right of landfall – most coastal structures can’t withstand that. This appears to be on par with Hugo.

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***Florence Update*** METMAN WEATHER SERVICES 7 Sep 2018 4:30 PM EDT

Please be aware if you live anywhere from coastal GA to New England. It’s looking more likely that Florence will intensify and make some sort of impact on the US East Coast by Thursday 9/13. At the current time, Florence could move inland bring heavy rains to South Carolina, North Carolina, and Virginia or turn north and act like a nor’easter. If you live in ANY eastern coastal areas or even several hundred miles inland from GA to southern New England I would advise watching Florence closely. Much can change between now and Wednesday but reduced shear, warm ocean waters, and merging with a disturbance south of Bermuda indicate significant intensification. Several caveats are the dry atmosphere in the mid and upper levels that could delay intensification and the exact extent of high pressure ridging in the Atlantic to the north. Climatology and historical analogs often push these storms to the N/NE but the strength of the current high pressure ridge could force the storm farther to the south and west before it turns north.

More info below:
Here is a summary from weathertrends360…

weathertrends360
7 hrs ·
If you live along the East Coast from South Carolina to Long Island you really need to monitor Florence! It went from a major hurricane to a tropical storm due to wind shear but it’s coming out of that shear now and very likely to again become a major hurricane this weekend passing to the south of Bermuda. The track has shifted more south and west which makes an East Coast threat more likely. With a huge blocking high pressure to the North there is no escape for Florence so the risk for a land fall along the East Coast is dramatically increasing for late next week (Thursday 13th).

The Euro model (posted in comments below) is showing a major hurricane hitting South Carolina Thursday. The US GFS 00Z says it’s a near miss off the New Jersey coast but the 6Z run this morning shows a devastating track through the Chesapeake Bay Thursday next week.

With water temps in the 80s off the East Coast (well above average) Florence will maintain strength as it nears the East Coast so this is looking more and more likely to be a significant event. It’s still 6 days away and track error can be 300 miles this far out but the overall blocking pattern to the north is very worrisome. Very large waves a certainty for most of the East Coast with 10-15+ foot waves without a landfall, more like 30 (right of landfall) if we do get a land fall!

Behind that the parade of storms coming off Africa is also impressive with at least 5 potential systems so the peak of the hurricane season looks to be extremely active as we go through September into early October.

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Forecasts 2018

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

Discussion of recent weather event 15-16 Nov 2018 Harrisburg, PA
There was most definitely was a shallow wedge of cold air. That really didn’t affect the forecast for snowfall other than it was cold enough at the surface to support accumulation. Actually it’s the warm air advection aloft that is arriving later than expected and to a smaller extent the slightly higher ratio (the snow was a bit drier than expected, possibly due to the colder air in the lower 2-3K ft). We all knew a shallow layer cold air would be at the surface thus the possible freezing rain scenarios. Entrenched cold air at the surface doesn’t play a big part in forecasting snowfall amounts unless it significant and deep but delayed warm air advection will cause more hours of snow and thus more accumulation Some of that accumulation will be lowered when mixing and rain come into play later and overnight.

In storm update:

***WEATHER UPDATE*** METMAN WEATHER SERVICES 1:05 PM EST Thursday 15 Nov 2018 Harrisburg, PA
Probably some alternate periods with more snow than sleet through this afternoon, then maybe a mix with some freezing rain later this afternoon and evening as more warm air aloft advects into the area and temps at the surface remain at or below freezing. As expected, the temp has dropped several degrees here (33.1° to 30.6°) with the advent of the precipitation.The afternoon and evening commuting will be horrendous. Later this evening around 8-11 PM, if everything falls into place, things gets better as temps as the surface warms just slightly, freezing precipitation begins to wane and we get mostly rain with some mix overnight. A lull or period of dry air intrusion (i.e. dry slot) can not be dismissed and a N to S oriented deformation band moving west to east may put down a quick coating of snow or a little more in the predawn hours as the low quickly pulls away to the NE. The rain, about a quarter of an inch, late tonight and into the AM hours Friday will wash away much of the accumulation leaving a messy slush in its wake. It appears that the low is intensifying a bit more than expected. QPF’s (Quantitative Precipitation Forecast) are now coming in at the high range of expected amounts meaning possibly a bit more accumulation in some places, especially in areas north and west of I81 and in higher elevations, but also in a few places in northern York, Cumberland and Adams counties. Storm appears to be over performing a bit more than anticipated yesterday morning as several impressive heavy bands have moved through and are moving through before the changeover. Based on the latest information snow for this afternoon expected to be 2-4″ in lieu of 1-3″ in most of York and Lancaster counties south and east. Some isolated areas to the south and east could get 5″ before the mix begins to erode the accumulation. Increase the areas north and west of those areas that I noted above to 3-6″ in lieu of 2-4″ with some areas slightly more before mixed precipitation hinders further accumulation. Expect mixed precipitation to arrive between 3 and 6 PM , generally from south to north. When sleet and possibly freezing rain arrive accumulations will diminished greatly and even lowered due to packing. Seems like the warm air will be a little slower to move in than I expected so we may get a few more hours of snow accumulation. Also snow is a bit drier (maybe 8:1?) than I had anticipated also. Both of these factors will lead to some additional accumulation before it gets significantly reduced by the mix and rain later today and overnight. Some areas farther west and north (areas in northern and western Perry, Mifflin and higher elevations) could get 5-7″. 2″ as of noon here in Enola. All that being said the final totals by Friday morning will be significantly reduced with the sleet, freezing rain and rain to follow. By Friday morning just 2-4″ of slushy accumulation will remain.

Updated total before mixing and rain reduces the totals:
South and east (southern York, Lancaster counties) 2-4″, locally higher
North and west ( northern York, southern Perry, Adams, Cumberland, Franklin, Dauphin, Lebanon counties) 3-6″, locally higher
Areas farther west and north (NW Perry, Mifflin, northern Franklin) and higher elevations 5-7″, locally higher

Here is my brief synopsis. The detailed analysis is much longer.

8:45 AM EST Wednesday 14 Nov 2018
I wouldn’t get too exited yet. Atmospheric thermal profiles are warming and forecasted snow amount based on a 10:1 ratio or Kuchera aren’t that impressive on the latest model runs. The ratio will most likely be more in the 5:1 or 6:1 range. The Euro, NAM, and GFS all show warm air advection above and below the 850 MB (~5K ft) level although the surface remains near freezing of even slightly below freezing. The deeper the warm layer the less snow we will get. Freezing rain may come into play in the afternoon and early evening hours. That would be a big concern. At this time I would estimate T-3″ in the local areas to the far south and east and 2-4″ for areas to the north and west for most of the lower Susquehanna Valley region. A few places farther north and in the mountains, especially farther west, could reach up to 6″. Obviously things can still change but the trend is now less snow and more mix after Thursday AM until mostly rain with maybe a wet snow mix and temps in the mid 30’s overnight and early Friday AM. I can send you my complete analysis if you’re interested.

***WEATHER UPDATE*** METMAN WEATHER SERVICES 8:45 AM EST Wednesday 14 Nov 2018 Harrisburg, PA (Detailed analysis)

Well here goes after spending several hours reviewing various models and atmospheric profile forecasts…here is my take at the moment. It’s a little too early to really tell with these types of system thus you have the mostly rain and mostly snow forecasts and everything in between. Any time you have energy transferring to a developing low near the coast many variables come into play. Much will depend on the transition, development, intensification, speed and the exact track of the developing low but in this case the timing seems to be pretty confident.. As with all intensifying low pressure systems the constantly changing dynamics will produce areas of heavier precipitation and possibly areas of dry air intrusion but the most important aspect of this particular system will be the atmospheric thermal profile. A small difference of several degrees could mean the difference of hardly any snow to possibly 6″ of snow. Initially, Thursday morning the atmospheric thermal profiles are mostly below freezing but expected warm air advection near the 850 MB level (~5K ft), depending on the thickness of the warm air layer, may cause some mixing and possibly some freezing rain later in the afternoon and early Friday evening if surface temperature remain at or below freezing. Initial atmospheric and surface conditions will support snow but as the afternoon wears on and into the evening those profiles become more marginal and more liquid precipitation with occasional sleet and snow mixed in as warm air advection first in the lower levels aloft near 850 MB and then near the surface later begin to erode any further snow accumulation with rain and mixing scenarios. Continued…

My concern is that the thickness of the layer of warm air with cold air near the surface (surface to possibly 900 MB or higher, ~3K ft or more) will result in sleet Thursday AM/early PM and then possible some freezing rain Thursday afternoon and early evening instead of snow. Simplified because a lot more is going on but generally if we get mostly snow you’ll know that the warm air advection aloft was minimal or the layer of warm air wasn’t deep. If we get some mixing and mostly rain you’ll know the layer was deep. If we get sleet and some freezing rain the layer was more than minimal but not deep enough to change the precipitation to rain. In any case later Thursday evening and Friday AM should transition into rain and wet snow mix. It’s likely that we will have several hours of light snow with mixed rain and sleet and possibly a little freezing rain if temperatures are cold enough at the surface Thursday afternoon/evening that will transition to just rain with pockets of sleet and a little snow Thursday night into Friday morning and then possibly ending with some snow as wind come in more from the N/NW pre-dawn Friday morning on the back side of the low pressure system as it moves away and eventually some scattered lake effect snows, mostly to the north and west, through the weekend. The Euro to some extent and the latest GFS and NAM show a deep layer of warm air advection that could mean mostly rain and wet snow throughout the day on Thursday severely limiting snowfall accumulation despite the colder air at the surface. Continued…

Snow in all likelihood will be wet and heavy significantly reducing model accumulations, which are based on a 10:1 ratio or Kuchera ratio, to more like 5:1. Ample moisture will be available throughout the forecast area as QPF’s are running 1″-1.5″ but in the local forecast area only about .1″ to .6″ of that precipitation should fall as snow with a ratio likely in the 5:1 or 6:1 range. Expect precipitation to start mid morning on Thursday and last to mid morning on Friday. Expect temperatures in the low 30’s in the AM or possibly even upper 20’s from evaporative cooling after the precipitation begins through afternoon then gradually increasing into the mid 30’s by later Thursday evening and overnight into Friday morning. That could also change somewhat as we get closer to the event. At this time I would estimate T-3″ in the local areas to the far south and east and 2-4″ for areas to the north and west for most of the lower Susquehanna Valley region. A few places farther north and in the mountains, especially farther west, could reach up to 6″. I’ll update later

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***Weather Update*** Metman Weather Services 6:00 PM EST 12 Nov 2018 (Local football games)
Rainfall expected in the 7 PM-10 PM time frame tonight:
Generally places west of Coatesville to Reading to Wilkes-Barre will get .1″ or less. Places to the east from Wilmington, DE north to Allentown and should get about .1-.25″. Areas east of that south of the turnpike and east of 476 and north of the turnpike along and east of the route 611 corridor (i.e. Easton, Doylestown, Stroudsburg, etc.) could get more than .25″, especially farther east near the PA/NJ border and NE of Philly. A few isolated spots far east along the border could receive up to .5″. The good news is that most of MOST of the heavy rain should be over by 7 PM in the western areas and by halftime or a little later in the eastern areas except the far eastern areas next to the PA/NJ border. The latest high resolution models show the heaviest rain is over for most by 8-9 PM except the extreme eastern region near the border. So expect conditions to improve slightly, at least as far as intensity is concerned, as the evening progresses.

Have fun and take plenty or rain gear, especially if you are in the eastern areas.

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***WEATHER UPDATE*** METMAN WEATHER SERVICES 9 Nov 2018 6:12 PM EST (Local football games)
Rainfall expected in the 7 PM-10 PM time frame tonight:

Generally places west of Coatesville to Reading to Wilkes-Barre will get .1″ or less. Places to the east from Wilmington, DE north to Allentown and should get about .1-.25″. Areas east of that south of the turnpike and east of 476 and north of the turnpike along and east of the route 611 corridor (i.e. Easton, Doylestown, Stroudsburg, etc.) could get more than .25″, especially farther east near the PA/NJ border and NE of Philly. A few isolated spots far east along the border could receive up to .5″. The good news is that most of MOST of the heavy rain should be over by 7 PM in the western areas and by halftime or a little later in the eastern areas except the far eastern areas next to the PA/NJ border. The latest high resolution models show the heaviest rain is over for most by 8-9 PM except the extreme eastern region near the border. So expect conditions to improve slightly, at least as far as intensity is concerned, as the evening progresses.

Have fun and take plenty or rain gear, especially if you are in the eastern areas.
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8/2/2018 Synopsis of game postponement on 8/1/2018 (Braves game)
As I continued to monitor the radar after the postponement, light rain showers finally exited the Smyrna area just before 9:30 PM. The batch to the SW slowed down began to slowly dissipate and show holes in the coverage by 10 PM. This cluster of showers moved through Douglasville continuing to diminish in intensity from moderate to mostly light showers by 11 PM and the eastern edge then moved through the Smyrna area with just very light intermittent showers continuing to dissipate between 11 PM and 12 PM . Only light showers at the ballpark after 9 PM and very little rainfall after 9:30 PM. They could have played but it is what it is and with both teams leaving town they probably just didn’t want to wait and see. I suspect that it was just some showers from the outflow boundary (https://forecast.weather.gov/glossary.php?word=outflow%20boundaryExternal Link)of earlier heavier showers and nothing related to any upper air disturbances. This mostly light shower cluster did hang around longer than I expected but eventually dissipated and brought very little rain to the Atlanta Metro area.
I checked this morning and here are some local rainfall totals last night after 9 PM and through 1 AM.
Marietta / Dobbins Air Force Base .04″
Atlanta, Hartsfield – Jackson Atlanta International Airport .02″
Fulton County Airport-Brown Field .06″
Cartersville Airport .05″

Definitely nothing that could not have been played through!

***WEATHER UPDATE*** Atlanta Metro Area 7:10 PM EDT 8/1/2018 (Braves game)
The latest RAP and HRRR are encouraging if they are willing to try. HRRR does bring in a showers just to the SE in the metro area between 8 PM and 10 PM and has been pretty consistent on that but has also been pretty consistent with just light rain until that time. Not sure I am a total buy in with that but hard to argue with that consistency. RAP is decreasing showers after 8 PM. The 22Z (6 PM local) RAP data just out is even more encouraging and the latest 22Z HRRR data is also more encouraging. It has some showers only between 8 and 9 PM and looks much lighter and less coverage than previous model runs although heavier rain (.25-.4″)is just to the east. It’s looking better than several hours ago for sure.

*** WEATHER UPDATE*** Atlanta Metro Area 3:15 PM EDT 8/1/2018 (Braves game)
Continued SW flow at the surface and aloft, abundant moisture and instability persist in the area. Convective development bringing scattered to numerous showers and thunderstorms throughout central and norther GA today. Several atmospheric short waves will propagate long a stationary front in the Mississippi Valley and the timing of showers and storms will be predicated on the timing of these pockets of instability. Mesoscale convective severe weather indices are slightly less impressive today indicating just moderate convection this afternoon and evening. An isolated severe storm is possible but any significant or widespread severe weather is low. Severe weather indices drop off considerably later this evening during game time.
I expect more widespread and somewhat heavier rainfall accumulations today (11 AM -11 PM) generally averaging about 1″-1.25″ by 11 PM but some area will pick up 2″-3″ and isolated areas even more. The steady SW flow aloft leads to the continual passing of showers and storms over the same area know as “training”. Some areas will experience that today while others will have more intermittent activity. The NAM, HREF and Euro push the axis of heaviest rain to the west and north today while the GFS has the axis more over the metro area and somewhat lighter rainfall. HRRR has the axis just east of the metro area although the latest 17Z data just in shows the axis moving to the west and 11 AM-11 PM rainfall amounts increasing to .5-.75″. HRRR has been persistent with some heavier rain (.5″) in the Atlanta Metro area between 7 PM and 9 PM.Once again activity should should diminish slightly as we move into the evening hours and between short wave pulses aloft but another disturbance will cause more showers to develop in the overnight hours (i.e. 3-5 AM). I’m skeptical of the GFS as an outlier but I should have a better idea with the 12Z Euro and the 18Z GFS and several more HRRR data outputs. I would expect the axis of heaviest rain to be west and north of the metro area but that doesn’t preclude some heavy showers in the metro area due to the close proximity of the expected axis. This would also agree nicely with my analysis and projected upper air dynamics.

Now for the important game time period. Confidence is not as high as yesterday but most models once again have the Smyrna area in the .1-.25″ range from 8-11 PM although several models do have pockets of .5″ through 11 PM but once again most of that falls between 8 and 9 PM and some between 9 and 10 PM. My only take from this is that we could be looking at a very similar situation to last night although the showers in the metro area could be a bit more numerous and extend a bit later into the evening before turning to intermittent and diminishing. In summary I would expect showers and a few thunderstorms to be scattered through 8-9 PM and becoming more intermittent after 9 PM. As far as the game goes it may depend on how bad they want to get it in. There may be a window to start but will most likely be a delay or we could just delay the game and start later in the evening but even then showers may extend a bit longer in most parts of the area and there is also the threat of light to moderate showers persisting or a brief heavy shower after 9/10 PM. I’m of the opinion now that there will be a window of several hours between 8 PM and 2 AM where we could play although that window may be interrupted several times with light to moderate showers, some maybe heavy enough to cause a delay possibly resulting in an AM finish.
Temps should be in the mid 70’s dipping to the lower 70’s and maybe even upper 60’s if some rain showers are present. Generally light winds, except during storms, blowing in from right/center at Suntrust Park. I’ll keep a tab on the radar and high resolution models to see if I can detect any trends that may reinforce or change my thoughts.
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*** WEATHER UPDATE*** Atlanta Metro Area 8:30 PM EDT 7/31/2018 (Braves game)

Some light to light moderate showers may move in about 8:40 PM. This is the very eastern edge of the MCS moving to the north. A brief moderate shower is possible within this area. They may hold together and move through but should be diminishing and through by about 9:15 PM at the latest and should be mostly light. If the game starts we should be able to play through these showers even though there may be brief moderate moments. After that, just light intermittent showers and an isolated brief heavier shower is possible but not probable through midnight.

*** WEATHER UPDATE*** Atlanta Metro Area 7:30 PM EDT 7/31/2018 (Braves game)

Showers and storms lifting northward but will persist for another hour or two becoming gradually lighter more intermittent as the evening wear on, especially after 8 PM. Some showers will also pass to the south moving to the NE Models are still in good agreement on the showers diminishing in intensity and coverage after 8 PM with residual intermittent showers hanging around for several hours but generally lighter and generally less than .2″ after 8 PM and most of that between 8 PM and 9 PM.. An isolated brief heavier shower after 9 PM is also possible. Showers are weakening at the present time and most should move through by 7:45 PM. Although intermittent light showers may persist, at the current time my best optimistic guess as to a possible start would be about 8:30 PM. The large Mesoscale Convective System (MCS) to the west in AL and western GA should mostly lift northward and gradually dissipate as we get later into the evening and overnight hours although showers could hang around there until well after midnight. I’ll watch the radar for anything new.

*** WEATHER UPDATE*** Atlanta Metro Area 1:25 PM EDT 7/31/2018 (Braves game)
While mostly cloudy conditions exist with the SW flow at the surface and aloft, abundant moisture and instability will increase this afternoon. Expect scattered convective development to occur this afternoon and early evening as enhanced dynamics during this time favor scattered showers and thunderstorms. Mesoscale convective and severe weather analysis parameters indicate moderate to isolated strong convection this afternoon, meaning some possible hail, heavy winds, and even some rotation aloft could be observed but the chances of widespread severe weather or tornadic activity is low. Expect some heavy shower and storms this afternoon over central and northern Georgia, .5″-1″ or more in some areas through 11 PM, but activity should wind down somewhat as we move into the evening hours, especially after 8/9 PM. I wouldn’t rule out a few showers, even some briefly heavy, or thunderstorms in the area after 8 pm but they should become more widely scattered after that time. Most models are indicating the heaviest rainfall before 8 PM but also indicate a general .1″-25″ and in a few areas up to .5″ are certainly possible after 8 PM although the dynamics will be less favorable. I sense from the models and dynamics that the heavier rainfall will be to the south and east and some possibly to the NW but that doesn’t preclude the Atlanta metro area from getting some heavy rainfall just that after analyzing the situation that is where heavier rainfall is more likely and widespread. Temps should be in the mid 70’s and maybe cooler as we get towards the 10/11 PM hour and generally light winds 4-8 MPH blowing in from right to across from right to left at Suntrust Park. I’ll keep a tab on the radar and high resolution models, especially HRRR, as we get towards game time.

 

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***Quick Weather Update*** METMAN Weather Services 3:25 PM EDT 22 July 2018

Several isolated cells are beginning to develop between the next mesoscale convective system (MCS) east of Richmond and the DC area. We could have some rain earlier than 6 PM and maybe by 5 PM if DC happens to fall in their path as they drift to the north.

***Quick Weather Update*** METMAN Weather Services 3:10 PM EDT 22 July 2018

Another batch of showers and storms has developed SE of Richmond and is moving north. If the current path and movement stay relatively the same the anticipated arrival time in the DC area is about 6:30 PM plus or minus 30 minutes. It’s difficult to tell the exact progression at this point as it also could shift either slightly east or west as it moves to the north. RAP and HRRR have picked up on this and have the 1 hour rainfall between 6 and 7 PM at about .25″. If it holds together I’ll have a better idea in another hour. Additional development northward and to the east and west is also possible.

***WEATHER UPDATE*** METMAN Weather Services 11:00 AM EDT 22 July 2018
The low pressure are that was responsible for yesterday’s rain tracked a bit farther west than anticipated increasing rain totals in the DC area dumping 2.5″-5″+ before ending early Sunday morning. Here in south central PA west of Harrisburg I measured 3.25″ in my gauge. That being said more rain is in store for the Mid Atlantic states over the next 4-5 days. Showers should begin to pickup around noon today and some heavy showers are possible this afternoon. This disturbance is moving in from the Ohio Valley in the wake of yesterday’s system. Once again the play-ability of today’s game is in doubt. Expect some heavy downpours and scattered thunderstorms with ~.25″ and possibly more depending on exactly where the heavier showers develop. Today’s showers and storms will be much more intermittent in nature today than the steady rain yesterday so there is some hope for baseball, albeit with possibly a rain delay or two, but periods of rain, some heavy, could linger for a while if it moves into the area. Models haven’t picked up on much more than .25″ yet (HRRR is currently at .5″ in some areas around DC) but given the dynamics it’s certainly possible that some places in the DC area could have .5″-1″ or even a bit more by evening. Scattered showers and thunderstorms will develop later this morning and this afternoon and will persist through the remainder of today and unsettled weather with showers and thunderstorms will remain through Wednesday. I’ll look at the radar before game time.

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***Weather Update*** METMAN WEATHER SERVICES 10:08 AM EDT 21 Jul, 2018 at Washington, DC (Braves game)
Weather looks very questionable for tonight. Timeline has been pushed back several hours as the developing low gathers steam. Steady rain will start between 10 AM and 11 AM in the DC area. Look for rain, heavy at times, and occasion thunderstorms, throughout the day. Precipitation may become a tad lighter and more intermittent this evening but probably won’t shut down entirely until very late, maybe around midnight. Expect a general 1″+ in the DC area today but the potential is there for 2″ or even higher amounts in areas that receive heavy downpours and multiple thunderstorms. After a dry start early tomorrow more showers pick up in the PM. Tomorrow’s precipitation will be more showery and intermittent in nature, but still could deliver some heavy downpours, with thunderstorms possible in the PM. Right now the greatest threat for heavy rain appears to be later in the afternoon, evening, and into the overnight hours but showers, some heavy, and a thunderstorm or two are also possible before that.

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***WEATHER UPDATE*** METMAN WEATHER SERVICES 5:10 PM EDT 26 Jun 2018 Atlanta Metro Area, GA (Braves game)
Once again a small upper air disturbance this afternoon and evening along with daytime heating will likely lead to isolated and possibly scattered showers, especially north and east of the Atlanta metro area. Scattered showers, generally .1-.5″, along the central and northern AL/GA border are also probable tonight but should stay well to the west until after midnight. The outlook is much more favorable tonight than last night. Global and regional models don’t show much in the Atlanta area for the game time period. The 12Z GFS and 18Z NAM 3K bear watching but are outliers and hinting at some showers (generally .1-.5″) from 8-11PM in the area but I think most showers should stay to the north and east of Atlanta through 10 PM. I’m not buying into amounts indicated by the GFS until I see the 18Z run and maybe not even then but a stray shower or two is certainly possible during game time. A slightly increased chance for showers exists as we move later into the evening and early morning hours. Otherwise expect temperatures in the mid to upper 80’s at game time to upper 70’s by 11 PM with a light WSW wind blowing out slightly towards left or across form right to left. Currently, HRRR and RAP also show only a marginal risk of any significant showers for the Atlanta vicinity for game time. I’ll give a radar update and check in on HRRR before the game.

***WEATHER UPDATE*** METMAN WEATHER SERVICES 7:20 PM EDT 25 Jun 2018 Atlanta Metro Area, GA (Braves game)
Definitely some showers and thunderstorms around this evening. I don’t see anything severe and indices don’t support any widespread severe weather. A series of small upper air perturbations this afternoon along with daytime heating has led to widespread showers and some areas of heavy showers and storms, especially to the south, is showing signs of more significant ridging later this evening, which should reduce the intensity in most areas as the evening progresses. The heavier showers to the south have moved east and decreased in intensity. Current shower coverage in the Atlanta vicinity and within a 50 mile radius is at ~70% as holes in the activity earlier have filled in with mostly light to moderate showers. Some heavy downpours are still possible and new showers (light to moderate) are currently developing to the west of Atlanta and moving east but the removal of daytime heating should aid in the eventual dissipation of shower activity later this evening. Showers could linger for several more hours over north central GA. Global and regional models are not picking up on much but HRRR 22Z gives the Atlanta area about .5″ this evening through 10 PM. I’m not buying into that much yet as the HRRR has been trending downward over the last several hours but .25″ and maybe a bit more if a heavier storm were to pass does look like a possibility. I’ll give a radar update and check in on HRRR as more data comes in over the next hour. It does look like at least a delay for a significant period while these showers pass.

RAP and NAM have now picked up on the precipitation and are expecting between .25-.5″. I think that’s reasonable and maybe a little high looking at the radar and expected intensities and length of showers. I just did a radar analysis looking at the intensity and expected length of the shower activity. I expect the showers to last until about 8:15 PM with possibly a few lingering lighter showers after that. The intensity and coverage should begin to lessen considerably by 8 PM. With the expected intensity to be moderate with intermittent light showers and gradually reducing to light after 8:00 PM. Using those expectation comes up to about .15″-.25″ of total precipitation through 8:30 PM. Hopefully play can start by 8:45-9 PM.

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***WEATHER UPDATE*** 24 June 2018 1:25 PM EDT Atlanta Metro Area (Braves game forecast)
Looks like some isolated showers will be around but most places in north central GA should remain dry. A small, narrow broken line of showers in western GA near Cedartown and stretching SW should be in the Atlanta area sometime after 3 PM (currently most likely between 3 and 4 PM). Could bring a few showers or even some thunderstorms if it holds together and enough sunshine is available for intensification and expansion. Regional models look good but HRRR is starting to pick up on the activity moving east from AL and is generating .1-.2″ of rainfall in the area between 2 and 5 PM while areas just to the rest could pick up .25-.5″ depending on the development and intensity. I’ll keep my eye on the radar (and HRRR) for any changes. Otherwise, just expect hot and humid conditions with temps in the low 90’s, heat indices in the mid to upper 90’s and west winds about 6-10 MPH. Wind may be a bit across from right to left but ball should carry well today towards left field if I have my orientation correct.-PA

GO BRAVES!

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*** WEATHER UPDATE*** METMAN WEATHER SERVICES 3:05 PM EDT 2 Jun 2018  Atlanta, GA Metro (Braves game forecast)
Just a low chance of showers later this afternoon and evening for the metro area north of I20 but can’t rule out a brief pop up type shower with a rumble of thunder given the air mass and instability indices. Activity in the metro area and points north will be generally isolated except for mountainous areas where orthographic lift could help generate a couple of stronger/longer lasting showers and thunderstorms that drift to the S/SE and eventually dissipate. Most activity should remain south of I20 and farther to the south where scattered showers are expected as atmospheric dynamics there are much more favorable. Should a shower sneak in, it should be brief and likely < .1″-.2″. Today’s game time frame (4-7 PM) will be hot and humid with temps in the mid to upper 80’s. Heat induces will be in the low 90’s and wind WNW 5-10 MPH ( that’s roughly out to left field if my orientation is correct). Tomorrow looks like a near repeat of today with slightly warmer temperatures and heat indices and also a slightly increase of an afternoon and/or evening shower or rumble of thunder. The ball should carry well today, especially center through left field, with the warm, humid air and a breeze blowing out to left.
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***WEATHER UPDATE*** 2:45 PM EDT 30 May 2018, Atlanta, GA (Braves game forecast)

Abundant moisture advection aloft from the SW in the wake of Alberto will bring in some low level clouds so any expected sunshine and associated instability should be limited today, at least until later in the afternoon. Cloudy and muggy conditions initially providing fairly stable air in north central GA early this afternoon should limit most precipitation activity to occasional sprinkles or very light showers but can’t rule out isolated development or enhanced Alberto remnant band providing a few showers but I expect most of that activity to stay to the south and west. Later this afternoon expect widely scattered showers and maybe a few isolated thunderstorms accumulating generally less than .25″ (and that’s a high estimate) unless an isolated heavier shower or thunderstorm were to pass through OR we get significant breaks in clouds that allows enhanced instability to build enough for a few heavier showers and thunderstorms later this afternoon and this evening. It’s also possible that outflow and the enhanced instability from dissipating Alberto mesoscale convection bands could redevelop to the SW this afternoon and drift NE enhancing shower activity and rainfall amounts (similar to circumstances that occurred last week). In the unlikely event that happens some possible marginally severe storms could pop up also as severe weather indices in metro area are marginally favorable for severe weather under enhanced solar induced instability and other favorable dynamics. In that case .25″-.5″ is possible but mostly BEFORE game time anyways. Just to reiterate, the aforementioned chance of heavy rain and any severe weather appear to be low at this time. HRRR is calling for some scattered heavier showers and thunderstorms but generally over-hypes expected convection in advance. It’s provides much more accurate forecast with established radar echoes within a few hours of impact. Even with the HRRR forecast of .5″-1″ in the area later today, the evening hours are quiet with very little precipitation showing up on HRRR after 5 PM.

CAPE (convective available potential energy) is moderate in north central GA while CIN (convective inhibition) is low so any process such as enhanced solar surface heating creating instability could lead to a showers and thunderstorms. The LI (lifted index) in north central GA is favorable for enhanced convective activity and thunderstorms are possible given the needed dynamics. Just thought I’d throw in a few atmospheric convective parameters there just in case you hear them sometime you won’t be totally clueless. An ironic situation is that low CIN in the morning could lead to heavy afternoon thunderstorms if CAPE is high enough and other indices are favorable. I don’t see that today…yet, as the instability needs created before the indices can be evaluated in those terms. CAPE is rising on several severe weather models but has been only marginal to moderate. I’ll touch on helicity and lapse rates sometime in a future post.

While PWAT’s (precipitable water in a column of air) are high (1.5″-2″) QPF’s (quantitative precipitation forecast) continue to lag in most models but a few do bring some heavy showers (.25″-.5″) into the area so it’s not out of the question for evening shower accumulating .25″ or a bit more but I see it as an unlikely scenario. Conditions for the game tonight should remain mostly cloudy, although breaks in the clouds are possible as the evening wears on, with just widely scatted showers generally <.1″ and mostly before 8-9 PM. IMO, some models are overplaying the precipitation today and especially this evening but I can’t rule out a brief shower or heavy shower or thunderstorm at this time but the chances are fairly low for any organized precipitation activity that could cause excessive delays or a postponement. Temps will be in the mid to upper 70’s and winds from the SSW 4-8 MPH. Looking ahead, plenty of tropical moisture and clouds will remain in the area throughout the rest of the week and weekend with increased shower and thunderstorm chances, especially Thursday and Friday, and still plenty of chances over the weekend then diminishing chances as we move into next week. Higher instability and slow moving storms could lead to some heavy rainfall as we move later into Thursday and Friday. I’ll check in before the game with a real-time update.
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***WEATHER UPDATE*** 3:45 PM EDT 29 May 2018
After isolated showers and thunderstorms this afternoon expect bands of showers and thunderstorms again this evening in north central GA. As the remnants of Alberto, now a subtropical depression, move into Tennessee late this afternoon the steering of shower bands over north central GA will set up more in a south to north pattern this evening so if you happen to be in one of those bands the activity could be persistent for several hours allowing for rainfall to accumulate. Most global and regional models are showing precipitation this evening to be .25″ or less. As a comparison, yesterday’s showers and storms produced between .3″ and .5″ between 7:30 PM and 10 PM in the immediate area. Most models have heavier precipitation setting up to the east of the metro area and especially in the mountains where orthographic lift could enhance rainfall totals. Some models have bands both to the east and west. HRRR, the most reliable short range model in these situations, has heavy bands to the east (Covington)and west (Douglasville) of the metro area but generally less than .2″ in the Smyrna vicinity. Once again, this is very inexact at this time and one of those bands could be slightly east or west making for heavy rain in excess of 1″ during the 7-10 PM time slot. An isolated cell not associated with the banding could also occur. The activity in north central GA should begin to wind down after 9 PM this evening. The feasibility of playing on time, playing with delays, or playing period (depending on how long they want to wait) will depend on the exact location and track of these shower bands. Otherwise, expect temps in the mid 70’s (lower if rain showers hit) and SSE winds at 8-12 MPH. Scattered showers and thunderstorms, some heavy, are likely again tomorrow afternoon and evening as more sunshine will create added instability. I’ll check with an update later.
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*** WEATHER UPDATE*** 1035 AM EDT 28 May 2018
Alberto began as an upper level low and is baroclinic in nature. Alberto has been starved of moisture from the dry slot has persisted through the night.That has kept the storm from strengthening but the movement has slowed and landfall isn’t expected until late Monday afternoon or Monday evening. After showers this morning, expect activity to change to intermittent widely scattered showers this afternoon as the dry slot will be directly over most of GA except the far SW portions. As the evening approaches chances increase for scattered showers and thunderstorms in the Atlanta area. Expect rainfall in north central GA to measure generally less .25″ during game time hours this afternoon so it’s looking somewhat favorable for game one. Those amounts increase to .2-.5″ for the game time period tonight so that’s not as favorable but not a definite rain out either…yet. If the storm stalls or movement slows the chances of playing a game two is greater. There is a distinct possibility that we could play both games even if Alberto continues at the current rate of movement but it’s extremely difficult to determine exactly where rain bands will set up. Even if the storm slows, some rain bands could push this far north. Looking at current model runs I’m cautiously optimistic at this time but concerned about development, banding, and moisture advection into the dry slot this afternoon and evening worsening conditions. I expect a slight general deterioration in conditions as the afternoon progresses and into the evening hours. Temps will be mostly be in the mid/upper 70’s with E/ENE winds generally around 10 MPH today and increasing late tonight. Later tonight/overnight and tomorrow heavier rains can be expected with locally heavy downpours. Conditions should begin to improve by Wednesday but scattered heavy showers could linger. Probably 2″ or more as a general rule before departing. I’ll be away at times today but will check in periodically with updates on radar and the latest high resolution model.
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***Quick Weather Update*** METMAN Weather Services 4:30 PM EDT 22 May 2018 (Braves vs. Phillies at PHIL)
Looking better for little to no rain tonight. Showers to the west are dissipating as they approach SE PA. For the game…Mainly cloudy with just very light precipitation/drizzle at times, especially early, if at all. Temps in mid 60’s and light winds. A front will move through overnight making for great weather tomorrow.

***Weather Update*** METMAN WEATHER SERVICES 3:45 PM EDT 22 May 2018 Philadelphia, PA (Braves game forecast)

Not much change from earlier except increasing looking like the showers, mostly light, may hang around until 7 PM. A lull in Philly now but expect light showers approaching from the west to enter the Philly around 5-6 PM and last until 7 PM. These look to be very light and should pass rather harmlessly. After that it looks pretty good. Any heavier downpours or thunderstorms should occur mainly before 7 PM but are really not expected. Clouds and lower temps have all but eliminated any severe weather chances. There is a slight chance of a stray heavy shower or a rumble of thunder of short duration after 7 PM but I’m only expecting mostly cloudy conditions with some occasional intermittent light showers and/or drizzle possible (< .1″) and maybe a bit of fog. Earlier the heavier rain stayed to the north, this evening the heavier rain should stay to the S/SE over New Jersey. Temps should remain in the mid to upper 60’s for the game time period. I’ll be away until around game time or later but I’ll be watching the radar and rapid refresh/rapid refresh high resolution models if I get back in time and post a short update. Wednesday looks to be very nice with highs in the low 80’s and little to no chance of rain tomorrow night with temps falling from the mid to upper 70’s at game time to the low 70’s/high 60’s by 10 PM with NW winds ~ 5 MPH.

***Weather Update*** METMAN WEATHER SERVICES 11:15 AM 22 May 2018 Philadelphia, PA (Braves game forecast)

Just did a quick look and the heaviest precipitation should pass north of Philly today. Light and occasionally moderate rainfall in Philly should pick around the noon hour or just before and continue intermittently throughout most of the afternoon with the heaviest being between 2 and 6 PM. After 6 PM, intermittent rain showers are possible through the evening hours with a chance of a heavy shower or thunderstorm during the game time period. Currently the 6 hour period between 5 and 11 PM models are indicating between .1 and .3″ but most of that is in the early part of the time period. Rainfall between 8 and 11 PM looks to be light (trace -.1″) except for the chance of a passing heavier shower/thunderstorm. Doesn’t look to be a wash out but can’t rule out a delay, especially if one of those heavier showers were to occur. I’ll look into more detail later today.

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***Weather Update*** 1:55 PM EDT 18 May 2018 (Braves game forecast)

After storms wiped out the final game of he Cubs series expect the moisture laden air mass to once again produce some scattered showers and thunderstorm today and maybe even a bit more coverage than yesterday. Vertical shear is weak so no severe weather is expected. Last evening’s heavy rains were a bit of a surprise as most models were lacking in identifying the energy available to produce them. The GFS had targeted the metro area but the time frame was earlier (5-8 PM) and the HRRR didn’t pick up on the the isolated cells via radar because they weren’t there yet AND they weren’t expected. Additional energy from an upper level trough and probably some low level mesoscale outflow convergence kicked off some isolated clusters between 7 and 8 PM and also helped the remnants of previously heavy showers to the SW remain viable for another 3-4 hours. Some rainfall observations over northern GA from the 8 PM- 2 AM time period showed .14″ in Marietta, .12″ at Hartsfield – Jackson Atlanta International Airport, .96″ at Fulton County Airport-Brown Field, Peachtree City .26″, Rome 0″, Milledgeville 0″, Lawrenceville 0″, Gainesville 0″, Cartersville 0″, so you can see the heavy rain was isolated in several smaller areas. Breaks in the clouds in places today will create instability once again this afternoon and dynamics similar to last night remain. Expect a general .5″ across northern GA today. A few areas could accumulate over 1″, and plenty of areas will have less than .5″ and some no rainfall. Models are projecting just slightly higher accumulations this evening over the metro area but scattered to widely scattered remains the theme with less than 50% coverage. There is some model agreement over a scenario similar to last evening but disagreement on the amounts. For the time period 8-11 PM the latest NAM and HRRR want to set up a band similar to last night with showers from the SW through the metro area and farther north with rainfall ranging from .1″ to a little over an inch with the highest amounts being south of the metro area. The HRRR has the majority of the rainfall before 8 PM while the NAM has it after 8 PM. The GFS sets up the area just slightly to the west (still includes the metro area) with .25″-.75″ and the RAP and Euro produce a similar scenario as both the GFS and NAM with rainfall a bit lower than the GFS (.1″-.5″). The GEFS solution is about .25″ with more in the NE part of GA. This is incredible model agreement and usually projects fairly accurately at least to the positioning if not the timing so I think we can exect some rainfall tonight in the area, however, in these types of setups it’s extremely difficult to determine an exact location on banding or isolated cell development so these models must be pretty sure the energy is going to be in these areas. My weighted blended model would have the metro are getting between .2″ and .5″ at some point between 7 an 11 PM this evening with some areas having higher or lower amounts but exactly where is hard to pinpoint. Current radar does show some development SE of Columbus but very little activity anywhere in northern GA. Once some radar returns start coming in from the afternoon and early evening HRRR runs I’ll have a more clear picture. Upper air support will gradually diminish over the weekend as these storms become more dependent on diurnal heating for instability but anomalously high moisture will persist and afternoon and evening showers and thunderstorms will likely occur over northern GA through at least midweek. I’ll be out for dinner but monitoring the radar afterwards hoping we can play some ball this evening.

Looking forward
Sat-Sun A general .5″-1″ over the weekend over northern GA with the heaviest generally being to the north. A few spots anywhere in northern GA, especially NE, could pick up 1-3″ and some areas could come up with less than .5″. No severe weather is expected this weekend.

GO BRAVES!

***Weather Update*** 7:07 PM EDT 17 May 2018 Atlanta Metro Area (Braves game forecast)
Daytime shower activity shows some enhanced instability and convective activity so a few storms may last a little later into the evening before they dissipate. A strong cluster of showers with embedded thunderstorms near and to the north of Hogansville/Grantville/Newnan and approaching Peachtree City has been producing some heavy rainfall is moving very slowly E/NE. Also several cells in a much smaller area near McDonough with moderate to moderately heavy rainfall are moving N along I75 and could affect the eastern Atlanta Metro area by 7:30 PM but they seem to be veering to the NE.. An isolated cell has developed just south of Roswell and is moving slowly northward and another isolated cell has just developed about 5 miles SSE of Smyrna. Several other isolated cells could develop over the next hour. I expect most of this activity to eventually dissipate as the evening progresses but wouldn’t be surprised if they lasted another several hours. Hopefully they miss the ballpark but those at the game may hear a few rumbles of thunder and experience enough rain to don their rain gear for a bit. In any case, a short delay is always possible with this type of widely scattered activity if it is heavy enough and happens to hit where you are at the time. It’s unlikely tonight but I’d give it a 25% chance. Watching the one just to the south but it’s pretty stationary and contracting slightly but I would expect it to eventually drift slowly N/NE. The one near Roswell is already beginning to dissipate.

***Weather Update*** 1:30 PM EDT 17 May 2018 Atlanta Metro Area (Braves game forecast)
Really not much change in the forecast from the last several days. Last night’s brief light shower didn’t show up as an accumulation in any nearby observation sites so I would surmise it was just a brief isolated event with no more than several hundredth’s of an inch. The low pressure system responsible for the showers over the last several days will move slowly to the NE. Diurnal heating and some upper level dynamics will produce enough instability to produce scattered showers this afternoon with a few thunderstorms in the mix. Rainfall this afternoon will generally be in the .1-.25″ range but most areas will remain rain free while others may get a bit more where heavier precipitation develops. The heaviest precipitation should occur across the northern tier and to the east today but an isolated heavy event can’t be ruled out in the vicinity of the Atlanta metro area. Currently, The current GFS model run is hinting at some heavy showers in the area before 8 PM (certainly possible) but very little after that and the HRRR from 8-11 PM but I’m not buying into that just yet. Like the last several days, the I see most of the precipitation winding down beginning in the early evening hours leaving just some widely scattered showers once again for this evening. Once again expect only about .1″-.2″ at most in some areas with many areas remaining rain free or just receiving a few very light showers similar to last night. There’s always the chance of an isolated stray stronger shower bringing in a bit more than expected (GFS/HRRR) but I wouldn’t expect anything over .25″ this evening unless something changes between now and then. Looking towards the weekend and beyond abundant moisture will remain throughout the weekend and into next week but upper air dynamics are lacking and most showers will be air mass type showers created by instability from the heating of the day (thermal convection) with areas receiving the most sunshine initiating more instability and heavier precipitation.

GO BRAVES!

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***Weather Update*** 3:30 PM 16 May 2018 Atlanta Metro Area (Braves game forecast)
After receiving as much as 1.5″ to 2″ today in the area more scattered showers are lingering with some thunder possible this afternoon, Some stabilization should take over this evening with just some scattered showers in the area as the low pressure area and associated tropical moisture move to the east. PWAT’s remain in the 1.5-1.75″ range so there is abnormally abundant moisture aloft just no trigger/forcing mechanism (i.e. front, upper air disturbance, convergence, convection etc.) to release it en mass tonight. Models are pretty much in agreement with keeping rain to the south and east this evening although like yesterday I can’t rule small rainfall amounts (.1″-.2″) over the course of the game if a stray shower or two were to sneak in but seems unlikely at this point.
QPF’s in some models for Thursday bring in another .5″ to possibly 2″ in a few areas including some thunder, heavier precipitation or multiple showers with the help of thermal lifting (convection) causing more instability but still nothing severe. Generally .25- .75″ for the area. This could change somewhat overnight so I’ll look at that tomorrow morning.

GO BRAVES… beat the Cubs!

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***Weather Update*** METMAN WEATHER SERVICES 3:30 PM 15 May 2018 Atlanta, PA (Braves game forecast)
Cloud cover will inhibit most convective development this afternoon over the metro area although a few scattered showers and an isolated storm is possible but should be short in duration and not severe. Indices reflecting the current dynamics just not showing enough to warrant severe weather. Currently due to some sunshine creating a bit of instability a few light to light moderate showers with a few rumbles of thunder are scatted to the south and east from Macon to Thomaston to LaGrange and farther E and NE through Athens and beyond. These should wind down later this afternoon and early this evening as instability weakens. Tonight’s game time frame should just have some intermittent light showers (~ .1″) with an isolated rumble of thunder possible especially S/SE of Smyrna. The NAM and HRRR are hinting at some isolated development and heavier precipitation closer to Smyrna just to the S/SE over the Atlanta metro area late in the game time period around 10-11 PM but generally I think most heavier precipitation and scattered thunderstorms should develop after midnight.

 

***Weather Update-First look***  METMAN Weather Services 11:15 Am EDT 15 May 2018 (Braves game forecast)
Looks like we may be able to play tonight. A low pressure area will provide plenty of moisture and cloud cover this evening but instability and other factors in northern GA aren’t clearly present in amounts to warrant severe weather but could develop so I’ll check later. PWAT’s (precipitable water in a column of air) are in excess of 1.5″ in the metro area so plenty of moisture. Afternoon heating may help to trigger a T-storm or two but the evening looks more promising for less activity until after game time. Most global models keeping the rain to the south but light rain isn’t out of the question. The NAM and Euro both bring in some light rain during game time with heavier rain just to the S/SE of the Atlanta metro area. HREF also brings in some light rain. Regional models (RAP, HRRR) are showing just some light precipitation but they will eventually incorporate radar returns for a more accurate outlook as we get closer to game time. 
GO BRAVES!

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***Weather Update*** METMAN WEATHER SERVICES 2:00 PM EDT 14 May 2018 Chicago IL (Braves game forecast- makeup game)
A quick meso analysis indicates that steep lapse rates will provide instability along with a lower level jet advecting later this afternoon and an upper level trough will provide the impetus for showers and thunderstorm later this afternoon and into the early evening hours. Most of the rain, especially the heaviest, will most likely occur after 4 PM but not ruling out some heavier showers possible before that as indicated by the 12Z HREF that could cause a delay. My weighted multi model solution (doesn’t include the latest HRRR run) indicates the most (and heaviest) rain will be after 4 PM and possibly after 5 PM. That would give us a window to complete the game. There is a smaller chance of up to .25″ 3 and 4 PM hinted by the HREF and GFS although the NAM keeps most of that to the north. On the positive side, the latest HRRR is pushing back the heavier showers to between 6PM and 9PM. The trend has been to push heavier showers later into the day and evening. The 17Z HRRR is coming in now and hopefully continues that trend. Looks like most of the rain moves out after 8-9 PM and instability weakens. Looks like we should be OK for a least 5-7 innings before things begin to get a bit dicey but there is that outside chance of a heavy shower before then. The current radar is absent of echoes but I expect them to start showing up within the next several hours.

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***WEATHER UPDATE*** METMAN Weather Services Sunday 15 APR 2018 1115 AM EDT Harrisburg, PA
Significant rain is probable late Sunday evening, overnight and into Monday morning. Until that time expect intermittent drizzle and light rain showers with intensity starting to pick up after 8 PM Sunday. Temperatures will hover in the mid 40’s Sunday and drop to the upper 30’s Sunday evening before warming overnight into the upper 40’s to even mid 50’s in some places by Monday morning before dropping with the cold front passage. Expect 10-20 MPH winds (higher in thunderstorms) from the east Sunday and eventually turning to the west Monday at 10-15 MPH. A deep column of moisture, frontal forcing, an inverted trough, and a short wave along with a strong 850 MB low level jet (~60 kts) will provide impetus for heavy showers and thunderstorms late Sunday night into Monday morning. PWAT’s are ~1.25-1.5″ and QPF’s range from a low of .75″ to a high of 3″ or more in isolated areas. The latest model runs have adjusted slightly upward or remained steady. Most models are showing the heaviest rain in the western half of the (Harrisburg-York line) forecast area. The most recent Rapid Refresh (RAP) model run indicates mainly 1.25″-1.75″ over the forecast area. Latest High Resolution Rapid Refresh (HRRR) runs seem to be somewhat higher (1.5″-2″). The latest Euro shows increase rainfall amounts of generally 1″-2″ east and 2-3″ west. I expect most areas to be in the 1.5″-2.25″ range (1.5-2″ east/south, 1.75-2.25″ west/north/central). Some areas will be in the 1′-1.5″ range (mostly east/southeast) and a few will be in the 2.25″-2.75″ range (mostly west/north/central). Isolated areas areas could come in at slightly less than 1″ (mostly east, a few south). Areas of heavier showers and storms could reach 3″ or a more (mostly west, north, central). A few heavier storms could develop to the SE later mid Monday morning before/as the cold front passes. The bulk of the rain should fall overnight Sunday night into Monday morning (midnight until 8 AM). Thunderstorms are possible generally between late Sunday evening until mid morning on Monday. Nothing severe is expected as severe weather indices are either nonexistent or marginal at best but strong wind gusts could occur. Light intermittent showers for the remaining portion of Monday may end up as a brief mix Monday evening.

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***IN STORM WEATHER UPDATE and DISCUSSION *** METMAN WEATHER SERVICES 9:15 PM 20 Mar 2018
3″ here as of 9 PM. As far as the storm(s) go I am also conservative initially when it comes to forecasting snow accumulation totals. Because of the model discrepancies I waited until this morning to even put together a forecast. Taking the time of year and other variables into consideration I was somewhat skeptical of the higher forecasts but I eventually capitulated to higher than I would normally go and went with 4-8″ north of the turnpike and 6-10″ to the south. I don’t think many could have foreseen 8-11″ in the far south central regions by dinner time Tuesday although it was pretty well known that they would likely see the most snowfall on Tuesday. I also anticipated an hour or maybe two of some mixing holding down totals somewhat. I could have maybe seen 5-6″ in some areas but surely didn’t expect the totals we got down there. I did include an enhanced snowfall line in my original forecast. I also thought there may be some mixing overnight tonight. I’m sticking with my original thoughts north of the turnpike and extending it south a bit and now think 8-14″ further south may be more likely due to the heavier snowfall there today. Here is the original narrative of my forecast this morning and updated with potentials several hours later.

1:15 PM 20 Mar 2018
Weather Update:
The dynamic potential (and moisture) is certainly there for areas, especially south of the turnpike and more likely along RT 30 and points south, to accumulate 12-15″+ if everything falls into place. HREF indicates some places could see 1-2″/hr snowfalls at times, especially south, Tuesday afternoon, and all areas could receive some moderate to heavy snowfall rates Wednesday morning into Wednesday afternoon. There will likely be a lull of lighter/no precipitation at times later this evening and overnight with some light snow and mixing from weak lower level warm air advection as the coastal low develops but intensities will pick up before daybreak and most areas will turn to all snow once again at some point Wed morning and continue at rates up to .5-1″/hr at times Wednesday between 8 AM and 4 PM. Some areas north of the turnpike could receive 8-10″+ depending upon any deformation banding and mesoscale forcing later in the event (Wednesday). There is also a possibility accumulations could be impeded in places, especially to the extreme southeast, by mixing overnight and early Wednesday AM keeping accumulations within the forecast range in those places. Like I said… a very difficult and challenging forecast.

9:45 AM 20 Mar 2018
Considering the factors involved, a general 4-8″ north of turnpike and 6-10″ south is reasonable. Thermal profiles support accumulations, especially on grassy and colder surfaces initially, due to a steep lapse rate from the surface to 1000 meters, and throughout the event although surface temperatures will be marginal at times. Expect 2- 4″ Tue, 1-4″ Tue evening and overnight, and 2-4″ on Wed. Brief mixing may occur Tue AM/early PM as the precipitation ramps up but evaporative cooling from any mixed precipitation will quickly change the precipitation to mostly snow. Later Wed evening the event(s) may wind up as a brief mix. Some mixing is possible throughout the entire event but mainly snow. Any significant mixing will hinder accumulations. Heavy snow due to mesoscale forcing and areas affected by deformation banding will see higher accumulations (2-6″) than forecast. Areas in the extreme southern part of the forecast area could receive more precipitation thus slightly higher snowfall amounts contingent upon the exact thermal profiles (i.e. mixing) in those areas. Some areas to the far north may receive less than 4″. Higher elevations > 200 meters will accumulate more snowfall than the surrounding areas.

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METMAN WEATHER SERVICES 2/7/2018

Perry, Dauphin, Cumberland, Adams, Lancaster, Lebanon, Berks local forecast for Wednesday 2/7/18
Tricky with the rain/snow line, exact track of the storm, atmospheric thermal profiles, timing of warm air advection. Currently, for the southern part of south central PA it looks like a coating to 2″ (isolated 3″ in northern areas near the turnpike) south of the turnpike & east of I81. 2″-4″ inches (isolated 5″) in a band about 20-25 miles wide north of that and 4-6″ (isolated 7″) further north (northern parts of Perry and Dauphin) and more further north and west. There could be a sharp cutoff in snow accumulations in places, especially near or to the south of I81/turnpike where you could have 1″ and 5 miles to the north you could have 4″. Should start between 5-7 AM as a mix/snow changing quickly to mix in the south and snow to the north. Expect the complete transition in the southern areas to occur between 10 AM and noon. Further north in the Carlisle/Harrisburg/Lebanon area expect the transition between 11 AM and 1 PM. In some areas, expect some sleet/freezing rain for a period before it turns to rain, especially to the south and east (Lancaster/Lebanon). Expect .1-.2″ of ice, especially south and east, before transitioning to rain. The warm air surges northward and most everyone is rain by 1-2 PM. Rain should wrap up by 5 PM except for far eastern areas (Lancaster, Lebanon, Berks) and extreme southern York where it may hang on until about 7 PM. Total liquid equivalent should be .5-.75″ in most areas and .75-1″ in a few areas while some isolated areas, especially north, may exceed 1″. Highs 34-38 north and 35-40 south, light E winds.

Forecasts 2017

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

***UPDATED WEATHER FORECAST*** METMAN WEATHER SERVICES 3:11 PM EST 11/8/2017 (for Fri 11/10/17 and Sat 11/11/17) Local Football Games

OK EVERYONE, LISTEN UP… PLEASE dress very warm for the Friday night football games! It is going to be extremely cold and some areas could still experience winds in the 10-15 MPH range with higher gusts making for a wind chill in the teens and even single digits in the colder areas like the Poconos. Generally the winds will be a little stronger to the east and in the Poconos.

East Central/East PA: Harrisburg thru Reading thru Allentown

Fri PM Hi mid to upper 30’s 32-38
Lo Sat AM mid teens to low 20’s 15-22 (record breaking lows in many areas)
Game time (7-10 PM) low 20’s to upper 20’s 22-30, NNW 5-10, G18 (winds and gusts may diminish slightly, 4-8 MPH G16, by game time in some western areas of this region)
Note: A few areas may be a bit colder and could dip into the upper teens by 10 PM

South Central/SE PA: Chambersburg thru York thru Lancaster thru Philly

Fri PM Hi mid to upper 30’s 34-40
Lo Sat AM upper teens to low 20’s 18-24 (possible record breaking lows in some areas)
Game time (7-10 PM) mid 20’s to low 30’s 24-31, NNW 6-12, G20 (winds may diminish slightly, 4-8 MPH G16, by game time in some western areas of this region)
Note: Some areas may stay in the upper 20’s while others will drop to the mid 20’s during the games. A few areas could drop to 20 or slightly below.

North Central/NE PA Williamsport, Sunbury thru Hazleton thru Scranton, Poconos and the northern tier

Fri PM Hi mid 20’s to low 30’s 24-32 (a few spots may get above freezing)
Lo Sat AM mid teens to low 20’s 14-22 (record breaking lows in many areas)
Note: Overnight some areas in the Poconos could drop to the low teens and even single digits are possible in some areas
Game time (7-10 PM) upper teens to mid 20’s 18-26, NNW 6-12 G20 (winds may diminish slightly, 4-8 MPH G16, by game time in some western areas of this region)
NOTE: Some areas, especially in the Poconos, could be in the upper teens at the start of the game and mid teens during the game with 10+ MPH winds and higher gusts.

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Jan 2017 Southern Snowstorm
Southern Storm Update: METMAN WEATHER SERVICES Fri 6 Jan 2017

Model Update/Discussion:The path of the southern storm has shifted slightly to the west in SC and NC. The North American Model (NAM) is calling for 6-10″ along the TN/NC border and the western NC mountains and up to 15″ in SE VA. The GFS is also very aggressive calling for 6-16″ in northern GA, the mountains of eastern TN and western NC and SE VA. The Canadian model is similar to both the NAM and GFS but downplays the TN/NC border ares snowfalls somewhat also. Currently most ensembles except the GEFS are downplaying the heavier overall snowfalls of the GFS and NAM. The Canadian model also slightly downplays the snowfall in eastern TN and western NC. I am leaning towards the GEFS ensemble, however, I believe it is downplaying the orographic effects and expected frontogenesis and moist geostrophic potential vorticity (MGPV) will lead to mesoscale snow banding creating areas of locally heavier snowfall throughout the eastern TN and western NC higher elevations. Once cyclogenesis in the northern Gulf begins this afternoon cold air advection will not be far behind. I’m leaning towards a blend of the GFS ensemble and Canadian models. As the storm strengthens I expect stronger winds Saturday in NE NC and SE VA in the 20-30 MPH range with higher gusts leading to blizzard conditions. Winds west and south of there will remain in the 10-20 MPH range.

Expect the heaviest snowfall to occur along a SW to NE line 100-150 miles SE and NW ( mostly NW) of a line from central Alabama (1-2″) to Atlanta, GA (1-3″) to Greeneville, SC (3-5″) to Charlotte, NC (4-6″) to Greensboro/Raleigh (6-8″) to Norfolk, VA (8-12″ with isolated higher amounts) and snow as far west as Knoxville and as far east and south as Augusta, GA and Columbia, SC and then northward to the west of the I 95 corridor in SC and southern VA and stretching east to the coast in central and northern NC. Snowfall amounts will decrease rapidly as you move to the south and east of these locations especially in the Al, GA, SC and southern NC areas. A slight delay in the arctic advance of cold air and cold air advection aloft will create a mix in western areas and a mix to mostly rain in eastern areas especially south and east of I20 from Augusta, GA and east of I95 in northern SC and into central NC and will significantly reduce snowfall accumulations in those areas especially east of I95 south of central NC. Areas in northern and northeastern NC are still expected to receive a significant snowfall of 5-10″ and possibly up to 16″ in isolated localities supported by QPF’s. Areas in northern NC and south central and SE VA are still expected to receive the heaviest snowfall and stronger winds/blizzard conditions.
Expect 1- 2″ from central Alabama (and maybe a little in central MS too!) to NE GA, with heavier amounts to the north and east reaching as high as 16″ in some localities in NE NC and SE VA. Expect 2-4″ in NE Georgia with 3-6″ totals with isolated higher amounts from NE Georgia north into eastern TN and western NC mountains. Expect just rain east of I 95 in southern SC and SE NC.

P.S. A blizzard warning has been issued for NE NC and SE VA as of 2:59 Friday Jan 6, 2017

***WEATHER ALERT*** METMAN WEATHER SERVICES Wed 4 Jan 2017
Several models are in agreement about a possible significant snow accumulation from west central South Carolina through central and eastern North Carolina and SE Virginia on Friday night into Saturday. Snowfall amounts could range from 2-6″ in SC and 4-8″ or more in east central NC. Accumulations in outlying areas of central and northern Alabama and central and northern Georgia could accumulate 1-4″ with higher amounts in north central SC. Models have been indicating this event for several days so probability is about 60%. The NAM model pushed the snowfall mostly into central NC and southern VA with snowfall generally in the 2-6″ range. Something to watch as we approach Friday and Friday evening. The most aggressive snowfall model(s) indicates a band of SW to NE orientation about 100-150 miles wide centered in central and eastern NC near Fayetteville and points 100-150 miles NE and SW of the there with the heaviest snow (over 4″ and possibly up to 8-12″ in spots). Other models are showing a more modest 1-3″ snowfall with isolated spots up to 8″. The infusion of arctic air into the forecast area on will ensure temperatures are cold enough to keep the precipitation mostly snow but it most likely will start as a mix later Friday and change to all snow overnight. Winds Saturday will be in the 15MPH range from the NW/NNW. Expect several very cold days to follow with highs only in the mid 30’s and low in the mid teen to lows 20’s. Temperatures should moderate by Tuesday/Wednesday. All this being said I would expect a general 1-4″ snowfall in the highlighted areas with 4-6″ with some locally higher accumulation up to 8″ from north central South Carolina SW of Fayetteville, NC into SW Virginia.

Models/Discussion As the southern storm moves up the coast a slightly more northerly course (i.e veer west) is trending and expected so areas near the coast and bay areas of VA and MD will see significant snowfall as will portions of NJ (3-6″), extreme SE NY and areas in close proximity to the New England coastline. The Canadian model downplays the expected coastal snowfall in CT and MA and the GFS exaggerates snowfall over eastern TN and western NC (8-16″), which is possible pending a secondary low and frontogenesis in that region favoring banding across that area. At this time I’m more inclined to agree with the slightly lower NAM amounts (6-9″) in that area. The NAM also picks up on the 8-12″ snowfalls in extreme SE MA so overall it looks like the best representation as of this time.

Summary:
Areas in south central and east central VA (4-8″) and coastal areas of VA and MD could get up to 12″ while coastal DE, NJ areas will total 2-8″ (more south). Areas to the north and west near DC/BAL/PHIL corridor are on tap for 1-3″. Extreme eastern regions of MA could get 12″ while CT and SE MA should get 4-8″ before storm exits to the NE. As expected, snowfall totals for eastern TN and western NC areas are increased to the 4-8″ range with isolated higher amounts possible. Little change to other forecast areas.Welcome to winter in the south!

Nor’easter Mar 2017 (with verification)

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

For weather fanatics here is a look at my predicted snowfall totals over the South, mid-Atlantic, and New England. Of course it’s impossible to look at all the localities and specifics of a local area, however, it gives a general view of forecast areas without delving into the anomalies associated with each specific locality.

Verification at bottom below forecast; forecasts move up the page in time.

Storm Update: MetMan Weather Services 3/14/2017 7:53 AM

It appears that storm is taking a slightly more westward track than originally anticipated and a bit of warm air advection has brought some mixing further inland. This will reduce accumulations over coastal areas and push mixing further inland from northern VA, DE, eastern PA, NJ and the New England coast. This includes but is not limited to areas in the I 95 corridor near the DC/Baltimore/ Philadelphia/Wilmington and into the New York City areas, SE PA, and especially southern and central NJ. If the track continues in this manner inland areas in southern New England as far inland as Hartford can expect mixing and somewhat reduced snowfall totals and significantly more rain in the coastal areas. Northern New England is still on track for mainly snow. Overall, the mixing line appears to be 40-80 miles farther NW than previously expected hindering accumulation significantly in those areas. Areas to the west and northwest with all snow/slight mixing are falling in line with most forecasted areas. A reduction of 4-6″ or more in areas that change to sleet/rain can also can be expected in many of those areas. On the other hand a slight jog to the northeast in the track would put New England on track for my original forecast estimates.
Locally, the slightly westward track and earlier warm air advection has hindered accumulations in SE York County, and central, eastern, and southern Lancaster counties. Any mixing in those areas should be turning back to mostly snow by 9 AM and some heavy snow banding can still occur over the next 3-4 hours to up the accumulations in those areas. Notwithstanding, expect those areas to come in with significantly less accumulation totals than the rest of the south central PA region.

Several model updates on possible total accumulations (Kuchera Ratio):

NAM 12Z (8 AM EDT): 4-6″ in SE areas affected by mixing, 6-12″elsewhere (this was putting out totals of 14-15″ with 30″+ yesterday)
GFS 6Z (2 AM EDT): 13-15″ SE, 13-18″ elsewhere, locally 18-22″ ( this was my main guidance for this storm)
RDPS mesoscale 6Z (2 AM EDT): 6-9″ SE, 10-18″, locally 18-22″
HRRR/Rapid Refresh 12Z (8 AM EDT): 4-6″ SE, 6-12″ elsewhere

As you can see many different totals even after the storm has started. Forecasting snowfall is not easy.

The mixing line appears to be 40-80 miles farther NW than previously expected hindering accumulation significantly in those areas. Areas to the west and northwest with all snow/slight mixing are falling in line with most forecasted areas.

3/13/2017 7:37 PM Final Update on impending coastal Nor’easter.

Storm Update:
Models/Discussion: Models in general agreement on the track thereby making some coastal and inland areas in northern VA, SE MD, DE, S NJ, and New England (coastal) susceptible to some mixing. The GFS has been the most consistent but the Canadian model is now falling in line. The NAM numbers are still substantially higher in a few areas in central PA through SE New York and bring more mixing into play slightly further inland but otherwise is reasonable. The Canadian model less so (mixing) and the GFS which displayed mostly all snow north of Virginia now shows more mixing inland and coastal areas of southern MD, DE, NJ, Long Island and some parts of New England, especially Cape Cod.
NAM and Canadian global and mesoscale model now pushes the heavier accumulation into NE PA, northern NJ and eastern NY. As a result snowfall amounts have been increased in those areas. As we get nearer to the storm itself the high resolution models will allow us get a better picture of the intensifying storm and deformation zones with heavier snowfall or possible dry slots reducing accumulations. The storm will develop late Monday or early Tuesday morning and intensify rapidly but will just as rapidly move up the coast and exit into the North Atlantic by Wednesday afternoon. Expect windy conditions on the order of 25-35 MPH or more with gusts to possibly 60 MPH or more in some places. Blizzard conditions will likely exist for at least 6 hours in some locations, especially from northern NJ into New England although points further south and inland into PA could experience blizzard or near blizzard condition also.
Templates have changed slightly to reflect greater detail in some areas. Mixing in SC, NC, central and southern VA, NE VA, SE MD, DE, and southern NJ will keep totals down or possibly even make it a mostly rain event in those areas. Coastal areas of New England, especially Cape Cod vicinity, could also be affected with mixing thereby reducing accumulation. Expect blizzard conditions in some areas, especially New England but also areas of N VA, DE, E MD, E PA, and NJ, early Tuesday (Monday night) through Wednesday evening as the storm develops and progresses to the north/northeast. I upped the central and eastern PA and inland northern NJ and SE NY several inches based on persistence of several global and mesoscale model guidance.

*Expect some additional accumulations, possibly T-3″, isolated 3-6” possible in the western North Carolina mountains (mixing probable, mostly rain east).

*Western VA: South 1-4″, locally 4-6”, North 4-8” locally 8-12″
*South VA: (except far west VA): Trace-2″, accumulations mostly west (mixing, mostly rain)
*Central VA: (except far west VA): Trace-6″, accumulations mostly west (mixing, mostly rain)
*North VA: (except west) 4-12″, locally up to 14″(some mixing possible, especially east & south, reducing accumulations), DC metro area 4-8” (some mixing likely)
*Coastal VA: Trace (mostly all rain)

*MD: (West) 6-12”, locally 12-16”
*MD: (North) 10-15”, locally 18-20” (some mixing/sleet possible)
*MD: Baltimore metro 8-10”, isolated 12” (some mixing likely)
*MD: (East) 2-8” (mixing likely)
*MD: (S, SE) Trace -1” (mixing likely, mostly rain)

*DE (North) 2-10″ (mixing, mostly rain south, snow north)
*DE (South) 0-2” (mixing, mostly rain)

*PA general except extreme SW PA: 8-20″, locally 20-26″
*SW PA 3-6″, locally 6-8″
*North PA 8-14”, locally 14-18”
*Central PA (south central PA) 14-20″, locally higher amounts of 20-24″ possible (slight possibility of some mixing/sleet, especially southeast).
*SE PA (includes Philadelphia metro area) 6-12″, 12-16” locally were mixing is limited (mixing probable, especially south, reducing accumulations)

*East PA/West NJ (North) 15-20”, locally 20-26”
*East PA/West NJ (Central) 15-20” locally 20-26”
*East PA/West NJ (South) 6-14”, locally 14-18” (some mixing probable reducing accumulations)

*NJ (inland, except west NJ) North 15-20”, locally 20-26” (mixing possible, extreme east)
*NJ (inland, except west NJ) Central 12-18”, locally 18-22” (mixing possible, east)
*NJ (inland, except west NJ) South 2-12″, locally 16” west (some mixing possible reducing accumulations, especially south & east)

*Coastal NJ North: 6-12″, locally 12-14” (mixing possible)
*Coastal NJ Central: 2-8”, locally 8-10” (mixing probable)
*Coastal NJ South: T-2″ (mixing probable reducing accumulations. Could be mostly rain)

*NY General: 12-24”, 24-30” locally (mixing extreme SE/east Long Island)
*SE NY 10-20”, 20-26” locally (some mixing possible extreme south/east Long Island, significantly reducing accumulations to 2-8”)
*New York City metro areas: 8-12”, locally 12-16” (some mixing possible)
*Central and North NY 8-16”, 16-24” locally
*West NY 8-12”, 12-16” locally

*New England General: 12-24″, locally 24-28″ (some mixing possible, especially near coastal areas and inland, reducing accumulations). Expect inland snowfall totals affected by mixing to be 6-12”, locally 12-14”
*Coastal areas of New England (except immediate Cape Cod vicinity): 6-14″, locally 14-18″ (some mixing likely reducing accumulations)
*Cape Cod: T-4″ coast, 3-6” inland (mixing probable, mostly sleet & rain reducing accumulations)

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3/12/2017 Update on impending coastal nor’easter (some areas in the Carolina’s have already been impacted prior to the coastal development).

Storm Update:
Models/Discussion: Models disagree slightly on the track thereby making some coastal and inland areas in northern VA, SE MD, DE, S NJ, and New England (coastal) susceptible to some mixing. The GFS has been the most consistent but the Canadian model has evolved but seems to be now be overstating accumulations. The NAM numbers are substantially higher also but present some interesting information. The NAM continues to bring more mixing into play in the coastal regions and inland in northern VA, SE MD, S NJ and even into SE PA. The Canadian model less so (mixing) and the GFS displays mostly all snow north of North Carolina.
Canadian global and mesoscale model hints at a heavy accumulation along the VA/W VA line into central and eastern PA that bears watching but recent mesoscale runs are more in line with the current forecast. As we get nearer to the storm itself the high resolution models will allow us get a better picture of the intensifying storm and deformation zones with heavier snowfall or possible dry slots reducing accumulations. The storm will develop late Monday or early Tuesday morning and intensify rapidly but will just as rapidly move up the coast and exit into the North Atlantic by Wednesday afternoon. Expect windy conditions on the order of 25-35 MPH with gusts to possibly 60 MPH in some places. Blizzard conditions will likely exist for at least 6 hours in some locations.

Templates have changed slightly and some have been merged. Mixing in SC, NC, central and southern VA, and southern NJ will keep totals down or possibly even make it a mostly rain event in those areas. Coastal areas of New England could also be affected with mixing thereby reducing accumulation. Expect blizzard conditions in some areas, especially New England, Tuesday through Wednesday as the storm develops and progresses to the north/northeast.

Expect some additional accumulations, possibly 1-4″, in the western North Carolina mountains.

Western VA: 2-8″ south, 7-14″ north locally up to 18″ north)
South VA (except west): Trace-4″ (mixing, mostly rain)
Central VA (except west): Trace-6″ (mixing, mostly rain)
North VA, including DC (except west) 8-14″, locally up to 16″(some mixing possible, especially east, reducing accumulations)
Coastal VA: Trace (mostly all rain)

MD (except SE): 10-15″, locally up to 22″
SE MD, S DE: Trace-3″ (mixing, mostly rain)

PA general except extreme SW PA: 10-16″, up to 24″
SW PA : 4-8″, locally 8-12″
Central PA through NE PA (including south central PA) 10-18″, locally higher amounts of 18-22″ possible (slight possibility of some mixing, especially east)
SE PA 8-16″ (some mixing possible reducing accumulations)

NJ (inland): 6-12″, locally 12-16″ (some mixing possible reducing accumulations)
Coastal NJ South: T-6″ (some mixing possible reducing accumulations. Could be mostly rain depending on track)
Coastal NJ North: 6-12″, locally 12-16″ (some mixing possible reducing accumulations)

NY General: 8-16″, locally 16-24″(some mixing possible, Long Island areas, reducing accumulations)

New England General: 8-18″, locally 18-22″ (some mixing possible, especially near coastal areas, reducing accumulations)
Coastal areas of New England (except Cape Cod area): 6-12″, locally 12-16″ (some mixing possible reducing accumulations)
Cape Cod area: 4-8″, locally 8-14″ possible without mixing (some mixing possible reducing accumulations)

Local South Central PA forecast:
Expect snow to arrive between 10 PM and midnight Monday evening with the heaviest snowfall between midnight and 10 AM Tuesday. Snow showers will continue over the area through Tuesday evening in varying lesser intensities. General snowfall amounts of 10-18″ with 18-22″ possible in certain localities that get heavier bursts. Possibility exists that some mixing in southern and eastern counties may hinder accumulations. Expect winds to be E-NE 10-15 MPH with gusts to 25 MPH shifting to N in the afternoon and NW in the evening. Low temp Sunday night.Tuesday morning the mid to upper 20’s and highs Tuesday in the low 30’s. Frigid arctic air will move in after the storm with highs only in the mid 20’s to upper 30’s with lows in the mid teens to around 20 until moderation over the weekend. Wednesday will be mostly cloudy with snow showers with a low in the low 20’s and temps rising only to the mid 20’s in the afternoon. NW winds pick up to 15-25 MPH with gusts to 35 MPH in the afternoon. Breezy conditions will persist Thursday into Friday.

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3/11/2017 update on impending coastal nor’easter:
I have devised a large area synoptic forecast template for the upcoming nor’easter snowfall likely to begin in the south early Sunday morning and continuing until departing New England some time on Thursday. All models are pretty much in agreement , however, there are some difference in accumulations and where mixing will occur based on phasing, time of cyclogenesis, exact track, and speed of the storm. In addition, local geographic formation inducing orographic lift and deformation enhanced zones will cause higher totals in some areas. Some have more mixing in coastal areas and further inland lowering accumulations but the general areas are pretty much defined. Expect blizzard conditions in some areas Monday through Thursday as the storm develops and progresses to the north/northeast. A more detailed model analyses will follow tomorrow.

Western North Carolina mountains and the Asheville area (to 50 miles east of TN border): 3-6″, isolated 8″ possible. (immediate Asheville area 1-4″).
Northwest and Northeast South Carolina and Southeast North Carolina: 1-4″ with mixing possible.
Central and Eastern North Carolina and Central and Southeast Virginia: Trace-3″ (some mixing likely)
Western VA: Trace-4″ south, 4-8″ north (isolated up to 12″ north)
Extreme Southern MD and DE (inland): 1-6″ (some mixing likely)
Coastal areas of VA, DE, and NJ: Trace-4″ (mixing likely)
PA except extreme SW PA: 5-15″, isolated 14-20″ (depends on track)
SW PA : 4-8″ isolated 8-12″
South Central Pa through NE PA and : 8-12″, isolated 12-18″
Extreme SE PA and inland NJ: 2-4″ or 8-16″ (depends on track)
Northern NJ (inland) 8-16″
NY: 8-16″, isolated 16-24″
SE NY: 16-22″, isolated 22-30″
New England General: 12-20″, isolated 20-26″
Coastal areas of New England: 4-12″ (need more data)

*********************************************************************

3/15/4:37 PM Verification of Snowfall Forecast for Nor’easter for 3/13/17 – 3/15/17

[Verification totals and comments are in brackets. No totals or comments generally means forecast was on or near the range forecasted.] https://www.facebook.com/weathertrends360/photos/p.1492110764135119/1492110764135119/?type=3&theaterExternal Link

MetMan Weather Services 3/21/17 8:41 AM

Verification of local forecast snow accumulation…

Verification rating and explanation:

[Here is the verification of the March 2017 Nor’easter (March 14-16, 2017) forecast.

Most regional snow forecasts were rated either satisfactory or accurate. In areas that did not at least meet the satisfactory standard, in almost all instances the reasons for lesser accumulations were noted in the original forecast narrative, however, the snowfall/mixing accumulations still fell considerably outside the forecasted range or contingent forecast range based on mixing or if no range was forecasted the snowfall totals were so significantly different than the verification totals that a satisfactory forecast rating would not be reasonable. This was due mainly to two factors.

  1. The storm took a slightly more westward track (about 50-75 miles).
  2. The advection of warm air in the lower levels, especially early on, allowed a mix of sleet and rain in some places rain to lower accumulations in the southern regions of the forecast area. Water equivalent forecasts were very much accurate.

The combination of these factors prevented more accurate or satisfactory forecasts in the southern and mid-Atlantic coastal and some inland areas. In addition, time constraints prevent advanced mesoscale analysis in all regions and localities.

37 Regional and Local Forecast Areas: 78% Adequate to excellent, 22% inaccurate
73% (27) rated Accurate/Good-Excellent
5% (2) rated Adequate/Satisfactory
22% (8) rated Inaccurate/Unsatisfactory

Legend:

🙂Accurate/Good Forecast
😐 Adequate/Satisfactory Forecast
🙁 Inaccurate/Unsatisfactory(busted) Forecast

End Verification Notes]

3/13/2017 7:37 PM Final Update on impending coastal Nor’easter.

Storm Update: 
Models/Discussion: Models in general agreement on the track thereby making some coastal and inland areas in northern VA, SE MD, DE, S NJ, and New England (coastal) susceptible to some mixing. The GFS has been the most consistent but the Canadian model is now falling in line. The NAM numbers are still substantially higher in a few areas in central PA through SE New York and bring more mixing into play slightly further inland but otherwise is reasonable. The Canadian model less so (mixing) and the GFS which displayed mostly all snow north of Virginia now shows more mixing inland and coastal areas of southern MD, DE, NJ, Long Island and some parts of New England, especially Cape Cod. 
NAM and Canadian global and mesoscale model now pushes the heavier accumulation into NE PA, northern NJ and eastern NY. As a result snowfall amounts have been increased in those areas. As we get nearer to the storm itself the high resolution models will allow us get a better picture of the intensifying storm and deformation zones with heavier snowfall or possible dry slots reducing accumulations. The storm will develop late Monday or early Tuesday morning and intensify rapidly but will just as rapidly move up the coast and exit into the North Atlantic by Wednesday afternoon. Expect windy conditions on the order of 25-35 MPH or more with gusts to possibly 60 MPH or more in some places. Blizzard conditions will likely exist for at least 6 hours in some locations, especially from northern NJ into New England although points further south and inland into PA could experience blizzard or near blizzard condition also.
Templates have changed slightly to reflect greater detail in some areas. Mixing in SC, NC, central and southern VA, NE VA, SE MD, DE, and southern NJ will keep totals down or possibly even make it a mostly rain event in those areas. Coastal areas of New England, especially Cape Cod vicinity, could also be affected with mixing thereby reducing accumulation. Expect blizzard conditions in some areas, especially New England but also areas of N VA, DE, E MD, E PA, and NJ, early Tuesday (Monday night) through Wednesday evening as the storm develops and progresses to the north/northeast. I upped the central and eastern PA and inland northern NJ and SE NY several inches based on persistence of several global and mesoscale model guidance.

*🙂Expect some additional accumulations, possibly T-3″, isolated 3-6” possible in the western North Carolina mountains (mixing probable, mostly rain east). [Generally 2-4”, isolated 6”, a few spots less than 2”]
*🙂Western VA: South 1-4″, locally 4-6”, North 4-8” locally 8-12″ [ Generally T-4” South, 4-6” North, isolated 10”]

*🙂South VA: (except far west VA): Trace-2″, accumulations mostly west (mixing, mostly rain) [Trace -1”, mixing /mostly rain]

*🙂Central VA: (except far west VA): Trace-6″, accumulations mostly west (mixing, mostly rain)
*🙂North VA: (except west) 4-12″, locally up to 14″(some mixing possible, especially east & south, reducing accumulations), DC metro area 4-8” (some mixing likely) [2-5”, N metro was in lower range]
*🙂Coastal VA: Trace (mostly all rain)

*🙂MD: (West) 6-12”, locally 12-16” [Generally 6-10”, isolated 12”, a few 4-5” far west, forecast range significantly intersects with verification range and verification mean is within the forecast range]   
*🙁MD: (North) 10-15”, locally 18-20” (some mixing/sleet possible), [Generally 4-9”, mixing, forecasted ranges don’t intersect, mean verification total significantly below forecast range despite mention of mixing]

 *🙁MD: Baltimore metro 8-10”, isolated 12” (some mixing likely), [2-7”], lot of mixing, mean verification amount significantly below forecast range and forecasted range did not intersect despite mention of mixing]     
*🙂MD: (East) 2-8” (mixing likely) [Generally 1-5”, extensive mixing]
*🙂MD: (S, SE) Trace -1” (mixing likely, mostly rain) [T-1”]

*🙂DE: (North) 2-10″ (mixing, mostly rain south, snow north) [T-5”, A lot of mixing but in lower range]
*🙂DE: (South) 0-2” (mixing, mostly rain) [T-1”]

*🙂PA general except extreme SW PA: 8-20″, locally 20-26″, [Less west and more east as expected]
*😐 SW PA: 3-6″, locally 6-8″, [Most were 1-3” but a few extreme SW were 6-8”]
*🙂North PA: 8-14”, locally 14-18” [Areas in NC PA were 6-18”, [much less NW PA was anticipated]
*🙂Central PA (south central PA): 14-20″, locally higher amounts of 20-24″ possible (slight possibility of some mixing/sleet, especially southeast), [Overall 9- 15”, S 4-12”, N 13-18”, a few spots of 20”+, Note: in the more specific local forecast a range of 8-12” was specified south and southeast due to mixing. Since forecast range outside the mixing area was accurate and the specified localized range due to mixing intersects with the verification range and the median forecast mean due to mixing falls also within the forecasted mixing range as well (only one is needed) and was reasonably within the specified area, the forecast is upgraded to accurate]
*😐 SE PA (includes Philadelphia metro area): 6-12″, 12-16” locally were mixing is limited (mixing probable, especially south, reducing accumulations), [3-8”, mixing/rain, mean verification total was near forecast range, verification range intersects with forecast range, verification accumulation range was significantly non-symmetric and/or skewed, and forecast narrative mentioned probable heavy mixing]

*🙂East PA/West NJ (North): 15-20”, locally 20-26” [12-24” isolated 30”, mean near center of forcast range and ranges intersected significantly.]
*🙁East PA/West NJ (Central): 15-20” locally 20-26” [4-12”, locally 14”, a lot of mixing lowered the totals here, mean and range forecast was too low.]
*🙁East PA/West NJ (South): 6-14”, locally 14-18” (some mixing probable reducing accumulations) [3-7”, mixing/rain, mean was near/just below bottom for forecasted range, and ranges intersected slightly and forecast called for mixing. Verification accumulation range was significantly non-symmetric and/or skewed (more west significantly less east, Could possibly updated to adequate based on narrative, slight range intersection, and narrative mention of mixing reducing accumulations but fell short of standard]

*🙂NJ (inland, except west NJ): North 15-20”, locally 20-26” (mixing possible, extreme east) [Generally 8-18”, isolated 20”+, several localized spots east less than 8” as described in narrative, region slightly skewed higher west, lower east, although mean fell slightly below forecasted range due to extreme mixing east (mentioned in forecast) the ranges did intersect enough to meet the satisfactory/good forecast standards.]
*🙁NJ (inland, except west NJ): Central 12-18”, locally 18-22” (mixing possible, east) [4-10”, mixing invalidated the forecast in this area]
*🙁NJ (inland, except west NJ): South 2-12″, locally 16” west (some mixing possible reducing accumulations, especially south & east) [T-3”, extreme mixing/rain. Mean fell near the forecasted range but ranges didn’t overlap enough to warrant a satisfactory forecast despite the mention of mixing and expected skewed/non-symmetrical accumulation were not present as all accumulations were at the minimum or lower than forecasted.)

*🙁Coastal NJ North: 6-12″, locally 12-14” (mixing possible) [1-4”, extreme mixing/rain]
*🙁Coastal NJ Central: 2-8”, locally 8-10” (mixing probable), [T-2”, mixing/rain, barely touched lower forecast range in highest accumulation areas even though probable mixing was forecasted extensive mixing and rain invalidated forecast.]
*🙂Coastal NJ South: T-2″ (mixing probable reducing accumulations. Could be mostly rain) [T-1”, mixing, mostly rain]

*🙂NY General: 12-24”, 24-30” locally (mixing extreme SE/east Long Island), [3”-25”, less west and more east as expected, isolated localities had 30”+, one place in NY had 42”…yikes!]
*🙂SE NY: 10-20”, 20-26” locally (some mixing possible extreme south/east Long Island, significantly reducing accumulations to 2-8”), [overall pretty close but a bit low, average totals slightly higher maybe 14-24”, small band of 25-30”, isolated 30”+, Long Island 3-5”]
*🙂New York City metro areas: 8-12”, locally 12-16” (some mixing possible), [4-15”, accumulation totals skewed/non-symmetric due to mixing that was mentioned in forecast but forecasted range and mean were accurate. Within 10-15 miles of central New York City accumulation of 6-10” in the borough, 4-6” south and east, 6-15” north and west were reported.]
*🙂Central and North NY: 8-16”, 16-24” locally [ 10-20” central, local 20-25” isolated 30”+; 15-25” north, local 30”+, some areas in west central and west northern had 10” or less, large differences most likely caused by orographic  anomalies]
*🙂West NY: 8-12”, 12-16” locally [6-10”mean, some places far west and south were 2-6” and others 10-15”, isolated 18”, while some places east and north were 3-6” or 10-15”, isolated 16-18”, large differences most likely caused by orographic  anomalies]

*🙂New England General: 12-24″, locally 24-28″ (some mixing possible, especially near coastal areas and inland, reducing accumulations). Expect inland snowfall totals affected by mixing to be 6-12”, locally 12-14”. [Generally 10-20” locally 20-25” with a few 30”+; generally 5-10”]
*🙂 Coastal areas of New England (except immediate Cape Cod vicinity): 6-14″, locally 14-18″ (some mixing likely reducing accumulations), [Overall 5-10”, 10-14” locally, mean and range are similar to or just slightly lower than forecast amounts; 2-6” south, coastal/slightly inland bays and inlets in southern New England , locally 8” (mixing/rain as expected); north, generally 8-14”, isolated 14-18” (some mixing) coastal/slightly inland bays and inlets (5-10 miles) in northern New England
*🙂 Cape Cod: T-4″ coast, 3-6” inland (mixing probable, mostly sleet & rain reducing accumulations), [T-3” throughout Cape Cod, mixing/rain, easterly storm track]

*🙂 Local South Central PA Forecast (Tuesday 3/14/17 – Wednesday 3/15/17): [Overall 9- 15”, S 4-12”, N 13-18”, a few spots of 20”+, Note: in the more specific local forecast a range of 8-12” was specified south and southeast due to mixing. Since forecast range outside the mixing area was accurate and the specified localized range due to mixing intersects with the verification range and the median forecast mean due to mixing falls also within the forecasted mixing range as well (only one is needed) and was reasonably within the specified area, the forecast is upgraded to accurate]
Expect snow to arrive Monday evening about 10 PM in southern counties and 11 PM in the Harrisburg area with the heaviest snowfall between midnight and 9 AM Tuesday. Snow showers will continue over the area through Tuesday evening in varying lesser intensities. General snowfall amounts of 14-20″ with 20-24″ possible in certain localities that get heavier bursts. Sticking mainly with the GFS guidance (with blends of mesoscale models) for snowfall as it has been consistent throughout. A few slight upward adjustments because of the global and mesoscale models that persist with enhanced snowfall amounts. A slight possibility exists that some mixing in southern York and Lancaster counties may hinder accumulations to 8-12” in those areas. On Tuesday, expect winds to strengthen. Expect winds E-NE 10-20 MPH with gusts to 30 MPH then shifting to N in the afternoon and NW in the evening. Higher winds in Berks County and eastern Lancaster County and points east will bring blizzard or near blizzard conditions to those areas. Low temp Tuesday morning are in the mid to upper 20’s and highs Tuesday in the low 30’s. Frigid arctic air will move in after the storm with highs only in the mid 20’s to upper 30’s with lows in the mid teens to around 20 until moderation over the weekend. Wednesday will be mostly cloudy, windy, and dreary with intermittent snow flurries and snow showers, especially in the afternoon and early evening. Temps rise from near 20 to only the mid-upper 20’s in the afternoon. NW winds 15-25 MPH with gusts to 35 MPH in the afternoon. Breezy conditions will persist Thursday into Friday.

MetMan Weather Services (local forecast and verification)

Verification of local forecast snow accumulation… ☺

Verification rating and explanation:

🙂 Forecast was rated as good/accurate due to advisement of lower accumulation totals due to mixing.

Verification Tuesday 3/14 -Thursday 3/16  [just under 4”, below the 6-10” forecasted due to mixing/rain but advised specifically that 2-6” was a possibility with significant mixing in the original forecast and the narrative contingent possibility was within the range of the verification amount or the mean of a localized contingent forecast was within the range of verification amounts and the forecast was reasonably within the specified area or locality, the forecast is upgraded to accurate.]

New Bedford, MA forecast (Nor’easter) Final Update 3/13/17 7:45 PM

Not much has changed. Right on the dividing line between Cape Cod where significant mixing should occur with snow but a lot of sleet and rain east of Buzzards Bay reducing accumulations significantly. I‘m still going with a total accumulation of 6-10″. If little or no mixing occurs 10-12″ and if significant mixing occurs then expect only about 2-6″.

Storm start early Tuesday AM (~6 AM)
Storm exits before midnight Tuesday although lingering snow showers and flurries may persist into Wednesday, especially instability snow showers Wednesday afternoon and evening. Little additional accumulation is expected.  Mostly snow Tuesday AM but some mixing Tuesday afternoon and early evening then turning back to snow before winding up. Temps will likely start in the low 20’s and peak in the upper 30’s to low 40’s. Winds from the E in early AM turning to N during the AM and then turning NW later in the afternoon. Sustained winds of 25-35 MPH and possible gusts to 60 MPH are expected. I am still going with a total accumulation of 6-10″. If little or no mixing occurs 10-12″ and if significant mixing occurs then expect only about 2-6″.

Wednesday will be cold, windy, and dreary, with snow flurries and showers starting in the low 20’s with highs only around 30. Thursday sun returns with highs 30-35 after a cold start of about 20, still breezy though with 10-15 MPH winds with heavier gusts to 25.

 

 

————————————————————————————–

Forecast Standards for verification of forecasts.

🙂 Accurate/Good forecast. Forecast range was pretty much on target or insignificantly high or low at the outside ranges. A narrative contingency forecast recognized, mentioned and included as a forecasted possibility or probability with a specific range (and area if mentioned) in the narrative, either above or below the actual forecasted range, that was verified by a mean within the narrative forecasted range or a narrative forecasted range that significantly intersects (ranges overlap significantly, normally by 25% or more in cases of mixing) the verification range, not including local extremes or anomalies. In large forecast regions with large disparities the mean verification amount was within the forecasted range or the verification range and significantly intersects (ranges overlap significantly) the forecasted range, not including local extremes or anomalies.

😐 Adequate/Satisfactory forecast. Forecast was correct in some areas but missed in other areas and the verification mean falls near the forecasted range or the verification range is significantly different but still slightly intersects (ranges overlap slightly) with the forecasted range, not including local extremes or anomalies, and the narrative recognized and mentioned possibilities or probabilities (contingencies), either above or below the actual forecasted range, but no specific range was forecasted.

🙁 Unsatisfactory/Busted forecast. Forecast was significantly different than the expected amount. The verification range fails to intersect (ranges fail to overlap) the forecasted range and falls entirely outside the forecasted range or the verification mean falls entirely outside the forecasted range, not including local extremes or anomalies, regardless if the narrative recognized and mentioned contingent forecast possibilities or probabilities, either above or below the actual forecasted range, with no specified range or if a contingent narrative recognized and mentioned a range of possibilities or probabilities, either above or below the actual forecasted range, and the verification mean falls outside the forecasted range or the narrative forecasted range does not intersect the verification range (ranges fail to overlap).

Forecasts 2016

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

*******************Weather Forecast 2/8/16 – 2/9/2016 **************

Discussion: 2/7/2016
Models generally indicate 6-8″ of snow north and west of I81 and 8-10″ south and east of I81. HRRR snowfall 5-8″ (10:1). QPF’s range from .6 to 1.2″ averaging about .8-.9, however, warmer initial atmospheric and surface conditions, mixing and lower snowfall ratios will likely produce less than models are indicating. As of 10PM it’s still 46 here in Enola.
There is little doubt about a snowy/slushy mess in the AM but the total accumulation is hard to forecast in this one.Totals are a little lower because it going to be warmer at first and then mixing and most likely a much lower than average snowfall ratio probably more like 5:1 initially but may wind up being close to 7/8:1 overall. Dynamics, lift and deformation banding favor some heavy snow periods in the hours just before dawn. QPF’s are .6-1.2″ depending on the model and forecasted model snowfalls are generally 6-10″ before taking other factors into consideration. Heavier accumulations may occur in isolated areas or areas that cool rapidly but warmer temps on roadways and other surfaces and a heavy wet snow equals less measurable accumulation. Cold air advection aloft will allow the snow to begin much before that cold air reaches the ground. Do not discount dry slotting, which is certainly possible in some areas, and will hinder snowfall accumulation significantly in those areas. Precipitation late Wed evening and early Thur AM will also provide evaporative cooling to lower the surface and near surface temps.
Expect 4-6″ just north and west of I81, 3-5″ in the vicinity of I81 and and 5-7″ south and east of I81. Expect isolated amounts more than 6″ in higher elevations in the vicinity of I81 north and east of HBG and some areas to the south and especially east of HBG. Expect 4-8″ in the mountains west and NW of HBG. To the east, heavier amounts of 6-10″ as you approach Allentown are possible and 8-12″ or more in points to the north and east into NJ, SE NY, CT and then SE MA. To sum up after considering various factors I’m expecting a general 3-6″ throughout most of south central PA with some areas of 6-8″ to the east of HBG and isolated areas of 6-8″ elsewhere. Snowfall will end by 7-9 AM in most places. Little change expected in next model runs.

Predicted Storm Snowfall Totals:
Mifflintown/State College 5″
New Bloomfield 5″
Carlisle 4″
Chambersburg 3″
Gettysburg 5″
York 5″
Harrisburg 4″ (Harrisburg verified at 5.3″ ~10:1 ratio) 3-6″ forecast
Lancaster 6″
Lebanon 7″
Reading 7″

 

Why do you say that? These are slightly lower than mine but snow accumulation totals contain several factors and accumulations also depends very much on the type of surface in an event of this type. There is little doubt about a snowy/slushy mess in the AM but the total accumulation is hard to forecast in this one.Their totals are a little lower because it going to be warmer at first and then mixing and most likely a much lower than average (10:1) snowfall ratio probably more like 7 or 8:1. Dynamics and lift and deformation banding favor some heavy snow periods in the hours just before dawn. QPF’s are .6-1″ depending on the model and forecasted model snowfalls are generally 6-10″ before taking other factors into consideration. Heavier accumulations 6-10″may occur to the NE, E and S or isolated areas with more may occur on areas that cool rapidly but warmer temps on roadways and other surfaces and a heavy wet snow equals less accumulation. Cold air advection aloft will begin the snowfall much before that cold air reaches the ground. Precipitation late Wed evening will also provide evaporative cooling to lower the surface temps. I would expect generally 4-8″ throughout the area. As always these amounts could change pending the next model run. I suspect these may be upped somewhat by this evening. Just my two cents!
Harrisburg verified at 5.5″
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Jan 2016 Blizzard

All weather forecasts are in chronological order from oldest at the bottom to newest at the top. Any forecast updates will be always be above the original forecast.

Officially 30.3″ fell in Harrisburg, PA on Jan 21-23, 2016
***WEATHER UPDATE*** METMAN WEATHER SERVICES Final Pre Storm Update: 1/22
Accumulations in NJ, eastern PA and New York City and points north may receive slightly higher snowfall totals due to a slight northward shift in the expected path of the storm. an additional 2-4″ could occur in most locations, which brings New England accumulations in the 2-6″ range and places like Boston 2-5″ and Providence 3-6″. All other snowfall forecast totals should have little changes.

***WEATHER UPDATE*** METMAN WEATHER SERVICES Final Pre Storm Update for Central PA: 1/22
In central PA, a more northerly storm path will cause slightly higher accumulations mainly north of the turnpike before the sharp cutoff line. Also, snow may arrive an hour or two earlier than projected. Other accumulations outside of PA remain in effect. Expect snow to arrive in the southern PA counties between 4 and 6 PM Friday spreading north into the Harrisburg area between 6 and 10 PM and lasting until roughly midnight on Saturday. A sharp cutoff in snowfall accumulations is expected north of I81/I78 and turnpike extended west of Harrisburg. Points immediately north of a line west along the turnpike towards Breezewood to Harrisburg stretching to I81 and I78 though the Allentown area can expect accumulations of 8-12″ with locally higher amounts. As you proceed further north expect accumulations to drop to 6-8″ and then 4-8″ and 1-3″ sharply as the snowfall cutoff seems to be in these areas. Places like New Castle and Lewistown will only receive 4-8″ while State College and east on I80 will only 3-4″. Localities in Perry county such as Duncannon, Neszport, and northern Dauphin county will most likely be in the 8-10″ range, less as you go north. South of the turnpike to route 30 expect 8-14″ west of the Susquehanna and 10-18″ east of the river. South of route 30 expect 10 -14″ west of the river and 12-18″ east of the river with isolated areas as much as 24″ east of the river near the MD border. Points near the border east of the Susquehanna will experience near blizzard conditions.

***WEATHER UPDATE*** METMAN WEATHER SERVICES Pre Storm Forecast: 1/21/16 update on impending nor’easter/coastal storm. Synopsis and general amounts for this event are as follows:

Most models have been pretty consistent, actually amazing, since this energy was far out in the Pacific. A significant snowfall will occur from central and eastern West Va, VA into southern PA, MD, DE, into NJ and the New York City area . Areas north of NY city will generally get less than 6″, mostly 1-4″ through eastern Conn, RI and MA. Mixing sleet and rain will occur along the DelMarVa peninsula and southern NJ holding accumulations down to generally between 2-4″ adjacent to the coast and 4-8″ for areas within 30 to possibly 50 miles of the the coast, however, as you continue inland snowfall amounts will accelerate quickly. Expect snow ratios to average about 10:1 slightly less if temps are in the upper 20’s or low 30’s and maybe about 12:1 with temps in the mid 20’s. Snowfall totals could move north or south somewhat due to the transfer of energy from the upper level low and exact cyclogenesis of the low off the coast and the track thereafter.
That doesn’t account for other unknowns such as dry slots, warm air advection (although this event should be mostly snow in south central PA, I can’t rule out some warm air advection mixing in non-coastal spots in eastern PA and NJ although it appears unlikely at this time), a secondary low developing off the coast, deformation bands and other convective areas that deposit heavier snow.

This is a dangerous storm. If you live in these areas forecast for heavy snow and wind please prepare now. Be advised that heavy winds will make blizzard conditions in northern VA, DC, central and northern MD, and possibly SE PA and SW NJ and winds of 15-30 MPH in other places will cause low visibility, blowing and drifting snow.. Coastal flooding is also likely with 25-35 MPH winds and gusts to 60 MPH with a full moon enhancing tides. Expect the brunt of the storm to be felt 50-100 miles east and west of the I81 corridor in VA and MD as far NE as the Baltimore/DC/Philly areas to 50 miles SW of Roanoke, VA. Accumulations in that area will range from 18-26″ with isolated locations receiving 30″ or more. Snowfall accumulations along the I95 corridor inland will range from 8-12″ in southern VA to 12-24″, more at you go north to just south of the DC metro area. Areas nearer to the VA coast will generally be 2-8″. Expect 20-28″ in the Baltimore/DC metro areas. As you continue north on I95 into the Philly area expect 14-18″ and 8-14″ north of Philly dropping sharply to 2-6″ in the Allentown areas and points north into the Poconos. Inland areas of central and western NJ can expect 8-18″ with NW NJ getting 12-15″ as you get inland towards the Delaware river. Expect 5-10″ in northern NJ west of New York while New York City accumulations will generally be in the 6-8″ range’. Accumulation at points north of New York City and northern NJ will decrease sharply receiving 6″ or less with just 1-4″ expected through Conn, RI, and into southern Mass, less as you move north. Expect only about 1-2″ in Boston and maybe 2-4″ In Providence.

Local South Central PA forecast:

Expect snow to arrive in the southern PA counties between 6 and 8 PM Friday spreading north into the Harrisburg area between 8 and midnight and lasting until roughly midnight on Saturday. I81/I78 and turnpike extended west of Harrisburg seems to be about where the sharp cutoff in snowfall accumulations begin to occur. Points immediately north of a line west along the turnpike towards Breezewood to Harrisburg stretching to I81 and I78 though the Allentown area can expect accumulations of 5-10″. As you proceed further north expect accumulations to drop to 4-6″ and then 2-4″ sharply as the snowfall cutoff seems to be in these areas. Places like New Castle and Lewistown will only receive 2-4″ while State College and east on I80 will only receive 1-3″. Localities in Perry county such as Duncannon, Neszport, and northern Dauphin county will most likely be in the 2-6″ range, less as you go north. South of the turnpike to route 30 expect 6-12″ west of the Susquehanna and 10-18″ east of the river. South of route 30 expect 8 -12″ west of the river and 12-18″ east of the river with isolated areas of 18-24″ east of the river near the MD
border. Points near the border east of the Susquehanna will experience near blizzard conditions.

***WEATHER UPDATE*** METMAN WEATHER SERVICES
1/20/16: Track has moved slightly north once again as we now have more available data over land. It still appears the worst is in southern PA, eastern W. VA, northern VA and MD and through the DC, Baltimore, Philly area but now New York and eastern New England come more into play.

***WEATHER UPDATE*** METMAN WEATHER SERVICES
1/19/16: For those in the VA, central PA, DE, NJ area a snowstorm still on track for mid Atlantic Friday PM-Saturday but latest models push heaviest snow slightly more south into the northern VA/DC/DE/S NJ Baltimore and Philly area. The models are still divergent over ridge amplification (i.e. the push of cold air from Canada) that ensures snow type precip but limits lifting and forces a southerly track and less well developed low pressure. Upcoming model runs after the upper level energy comes onshore from the Pacific should provide much more insight as to the exact track and strength of the developing low over Tenn valley. Track could lift back to the north or continue to slowly track south. A sharp heavy snowfall cutoff line is expected. New York may be affected and New England can’t be ruled out yet for this storm.

***WEATHER UPDATE*** METMAN WEATHER SERVICES 1/18/16 12:32 PM EDT
Models coming into agreement on major northeastern storm though it’s still early. Currently northern Virginia though central Maryland and into central PA is worst prog. 8″-24″ or more possible. Still some questions on the exact track, blocking high ensuring cold air, and sometimes the energy from these west to east moving storms jumps to a coastal low leaving some places with lower amounts depending on the dynamics of the atmosphere and the development and exact location of the coastal low. Updates coming.

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MetMan Weather Services provides meteorological information, services, advice, and solutions for the discriminating user by using established applied meteorological and climatological methods. Synoptic, mesoscale, and microscale analysis are done to provide and ensure dependable operational, atmospheric, and environmental forecasting solutions. Services include South Central PA weather forecasts plus synoptic, mesoscale, and local forecast summaries, synoptic, regional, and local snowfall accumulation forecasts, upper winds forecasts, weather radar/severe storm monitoring services, atmospheric analysis, including thermal profiling and Skew-T analysis, numerical weather model information, discussion, and analysis, travel planning, and climate analog information. Best of all these services are provided free of charge to clients, friends, and business associates. MetMan continues to enjoy meteorology and climatology in retirement and is now able to do it as a hobby rather than a paid occupation. As time permits MetMan hopes to pass along meteorological and climatological knowledge, advice, and information that may be useful to others.

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Mike (aka Metman) is a retired meteorologist, a former NOAA-National Weather Service employee, and a former employee of the DOD’s U.S. Army Atmospheric Sciences Laboratory where he was an associate RDT&E meteorologist at White Sands Missile Range, NM, Poker Flat Research Range, AK, and eventually the Chief Operational and Research Meteorologist at Yuma Proving Ground, AZ. As a NOAA employee, Mike was a certified NOAA-NWS Weather Radar Operator, Weather Observer, Weather Forecaster, and Climate Data Analyst. Mike was also a certified DOD weather forecaster specializing in operational, environmental, and ballistic weather forecasting, military meteorology, planetary boundary layer, aeronomy (middle and upper atmospheric research), and meteorological research and project support (RDT&E).



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