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It's early, but might as well do the annual severe thread (people were talking about it in the long range thread!). I don't have the @WxWatcher007 scale handy on this computer - but I usually post it for posterity for the upcoming severe season. Anything from discussing past events to potential upcoming patterns/analogs, and discussion about more specific upcoming threats can be posted in here. A while ago we stopped doing event-specific severe threads for most things. Whether we do that or not - this is the general thread. Have at it!
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The boring season continues here but the first two weeks of Met summer look favorable as far as us not roasting goes. The 6-10 day and 8-14 day outlook favors BN temps and near to bn precip. The first two days of met summer have produced low 70s yesterday and only mid-60s at 1pm here with rainfall both days. The countdown is on until the first true cold front of fall.
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Given that there is a tiny chance at something next week, we'll go ahead and open up the 2023 iteration of the thread. I doubt it will amount to much of anything (perhaps a better chance in the Carolinas and far SEVA) but we'll see. General mid to long range discussion can go in here, as can discussion about past events etc. In past years this has also served as a bit of an "on the fly" obs thread for events that are too small to warrant a separate thread. Pretty casual rules in this annual thread. Looking forward to our usual folks And as always - attached is the @WxWatcher007 tier system for our severe threats here in the Mid-Atlantic subforum.
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Now the dreaded season (for me) is upon us. Heat, storms, flooding and waiting on that first cold front in September to arrive and seeing those first lows in the 40s. I don't know what the summer will bring, but we know it will be hot and humid. Severe season is already off to a bad start with the tornado outbreak that spurred a lot of fatalities last week. I know it can't be avoided but I hope we don't have any more this spring.
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More heat, humidity and thunderstorms?? Go!
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Meteorological Spring hits March 1st, thus begins the quiet season on the forums. This thread should suffice until fall for any long range disco. I doubt the last flakes have fallen this year but I don't really expect another widespread winter threat either. It was definitely a Plateau to Western Tennessee winter. Tough for Eastern areas not to do any better with virtually the entire month of January being BN for temps. The flood threat, as it always seems to be these days, is definitely elevated again this spring. The severe threat, I'll leave that to Jeff, Jax, and the rest of the severe gurus. -
We're turning this into the TIMS thread. Thunder in the mountains model? Can it equal snow afterwards? If so, does severe weather = heavier snow? We'll know by January 3rd, lol. -
SPC continues Marginal risk se NYS-NJ. 00z-06z/20 HRRR/NAM/EC have decent development Wednesday afternoon. TT near 53 flag attention for hail and gust transfer looks like 40-45KT. Follow NWS local offices/SPC/and our own members assessments. Have added the SPC discussion plus the EC (just below SPC)/GFS (below EC) fcst sounding for 18z/21 n central NJ as an idea of what seems to be coming via convection for NJ. CAPE is marginal and KI OK. Activity while still fairly strong crossing LI/CT will ingest cooler southerly inflow from the ocean to limit potential hailers/wind gusts? Even so, the wind shift with significant cold air advection during the evening may induce isolated gusts 40 kt on the island? Have a look. This thread should also serve well for any significant reports of whatever convection occurs Wednesday afternoon. -
It's March...and even though we probably have a few more winter weather threats ahead...it's time to launch the 2019 Mid-Atlantic Severe Wx thread. Pattern stuff can go in here, discussion leading up to events and more. Same guidelines as past years. Thread will probably idle for a month or two - let's hope for some general excitement this year.
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I have been really slacking as of late on the blogging ... hoping to fix that! Mediocre line of storms developed over the central Shenandoah Valley this afternoon and prompted a local blue box from Sterling around Charlottesville. There was a single report of wind damage in the city limits as well ... so congrats Sterling on the verification. Another line of storms lies further west from west-central Illinois through IND and down into LEX/central Kentucky ... high level blow off from this activity will likely stay clear of the area in at least the near term and allow for good rapid west to east clearing this evening. The clear skies early, excess moisture, and generally light winds will set the stage for some patchy overnight and early morning fog in areas that saw rain this afternoon (mainly the KSHD/KCHO area). This is not really anything new as this general area has seen patchy fog the last several mornings.
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Hail can be a weather enthusiast delight during the Summer time (perhaps it reminds them of snow?). Unfortunately, forecasting hail size can be a bit of challenge. One method that I use is VIL Of the Day (VOTD). It was developed by the NWS back in the 90s. It purely relies on temperatures aloft and while simple, does a surprisingly good job. Obviously there are some limitations, but I will get to those in a minute. The calculation is straight forward and is as follows: VOTD = 750 / [(h5T+h4T) / 2] where h5T and h4T are the absolute values of the 500mb and 400mb temperatures respectively. The VIL value given from this equation is the approximate value at which you can expect 0.75” diameter hail stones to fall. 0.75” was chosen because this used to be the hail criteria for a severe thunderstorm. For operational purposes, the lower the expected VOTD the higher the large hail potential you can expect. I like to use 40 g/m^2 as a rough baseline in the Summer time. For those that are not familiar with VIL (Vertically Integrated Liquid), it is a radar product that operational meteorologists use to locate areas of heavy precipitation and hail. It is available in real time in all GR-LevelX products and some places on the internet (Weather Underground, etc). See the wiki page for a brief overview. Now back to the limitations of the VOTD approximation. It is best used for regular thunderstorms and not those with established mesocyclones (i.e. supercells) … although honestly it still works fairly well on most supercells we see around here. In storms with well-organized and established mesocyclones, there are additional mesoscale lifting mechanisms at work that can work to produce huge hail more efficiently than what you would tend to find in your average non-supercellular severe thunderstorm. Keep in mind that the VOTD can change as the thermal profile aloft changes. Check forecast soundings (remember, there is more than 1 model) for the afternoon ahead instead of relying solely on the 12z observed soundings. Lastly, VOTD gives you the VIL value for 0.75” hail stones and tells you nothing about maximum hailstone size, etc. I have attached a calculator that I wrote to help me compute VOTD quickly. I wrote it a while back, it’s ugly, it’s written in FORTRAN, but it does the job! votd.zip
