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2013 Mid-Atlantic Severe General Discussion


Kmlwx

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That new SPC site is pretty awesome though. Just looking through the distributions (which you can break down by cold season, QLCS, etc)... how things differ by region etc. Can get lost in there for a while I'm sure. Should be helpful for forecasting too with the easily identifiable benchmarks.

Yeah I had to stop myself the other day when I was looking around on it. I almost made myself late for a class. 

I've always liked the NCDC storm database too - good starting point if you are trying to find storms in a specific jurisdiction. 

Can't wait for a morning when people are going ape**** over the 12z LWX sounding. Then nothing will happen...

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Nice Ian... thanks for those.

 

This would be a frightening scenario if it were to repeat -- http://www.tornadohistoryproject.com/tornado/19790905.51.7

 

EF3 crosses the Beltway twice... at rush hour

I have to assume that is just peak intensity. I'm sure the EF3 intensity was fairly short lived. Wasn't the EF4 in La Plata like pretty much just a few blocks in town? (not downplaying that incident)

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I have to assume that is just peak intensity. I'm sure the EF3 intensity was fairly short lived. Wasn't the EF4 in La Plata like pretty much just a few blocks in town? (not downplaying that incident)

Probably, the link doesnt specify.  But even if that was so, a tornado crossing the Beltway regardless of its EF strength would be a dangerous proposition

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I've always liked thunderstorms - as kids, we used to sit on our west-facing porch under our aluminum awning and watch as big boomers rolled in. And I think I like them as much, if not more, now. I've never really looked forward to severe season around here, but for some reason I am looking forward to it this year. I don't know if I like the storms themselves or just the idea that we're moving out of such a miserable time of year and into the growing and outdoor activity season. Hopefully I can learn a little more about severe this year, because I frankly have no clue about the meteorology behind it!

As for hail...screw it. Larger hail would mangle my garden, so someone else can have it!

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First threat of the season already.. Looks to be mainly a high wind event.

 

LSyJkG5.png

 

 

 

VALID 301200Z - 041200Z      ...DISCUSSION...   THERE IS REASONABLE AGREEMENT AMONGST THE LATEST SUITE OF GUIDANCE   THAT A POWERFUL AND HIGHLY AMPLIFIED UPPER TROUGH WILL MAKE RAPID   PROGRESS TOWARD THE ERN SEABOARD THROUGH LATE D4/WEDNESDAY. A MID   LEVEL WIND MAX IN EXCESS OF 100KT IS FORECAST TO ROTATE THROUGH THE   BASE OF THE TROUGH FROM THE TN VALLEY TO THE MID ATLANTIC COINCIDENT   WITH THE ADVANCING COLD FRONT ACROSS THESE AREAS. MODELS ALSO   SUGGEST THAT LOW AND DEEP-LAYER MOISTURE WILL INCREASE RAPIDLY   IMMEDIATELY AHEAD OF THE FRONTAL ZONE WITH ECMWF DEPICTING A PLUME   OF AT LEAST 1.5 INCH PW VALUES EXTENDING AS FAR NORTH AS PHL AREA BY   WEDNESDAY EVENING. QPF AND VERTICAL MOTION FIELDS FROM LATEST EC AND   GFS MODELS SUGGEST A CONTINUATION AND/OR RESURGENCE OF CONVECTION   ALONG NEARLY THE ENTIRE FRONT AMIDST INTENSE CLOUD-BEARING SHEAR.   WHILE CAPE ACROSS MUCH OF THE RISK AREA WILL REMAIN LOW...EXPECT   BOUNDARY LAYER WARMING/MOISTENING TO BECOME SUFFICIENT ENOUGH TO   SUPPORT THE DOWNWARD TRANSPORT OF HIGH MOMENTUM AIR TO THE SURFACE   WITH DAMAGING WINDS EXPECTED TO ACCOMPANY THE PASSAGE OF THE   CONVECTIVE LINE.
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A widespread strong to severe wind event appears to be unfolding over the eastern half of the U.S. Tuesday into Wednesday, with isolated tornadoes also a threat, which is mostly across parts of the Southeast. The Mid-Atlantic has some opportunity for both on Wednesday, with the main threat obviously being a line of strong to severe winds.

We will be battling marginal lapse rates and pre-frontal clouds/rain, as we normally do in these early year setups. Very strong winds aloft (50-60 kt jet at 925mb!) suggests any sort of convection will bring down strong to severe level winds. With the strong forcing associated with the cold front, I don't see much of a problem getting those winds to the surface. The only issue would be if a stable layer at the surface can linger ahead of the front, but that appears to be just a minor problem as the lift from the front should overcome the stable layer (if there is indeed a stable layer).

With dewpoints climbing into the lower 60s ahead of the front, we should be able to see a fairly strong frontal passage with widespread strong to severe winds. The main thing I'm watching now is the potential of a secondary low formation, which the NAM has (though that can't be relied upon at this point). The Euro also develops a secondary low, but it comes later and further north than the NAM. If this secondary low develops before the front comes through, and if it's far enough south, it will be able to back the winds more at the surface and would provide a greater risk for tornadoes in the Mid-Atlantic.

post-96-0-79133800-1359302062_thumb.png

post-96-0-61476900-1359302148_thumb.png

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Only trouble with backing the winds with the low developing farther to the south is it inch increase the chances of a stable layer messing things up to the north of that low.  Heck, the Nam already has the surface RH near 100 percent on Wednesday which opens the possibility of fog messing things up for us here in the DC area though I'm not sure that would stop gusts from reaching the ground. I do think it would hurt our chances of getting tornadoes due to stability issues but you're more a severe weather guy than I am.  There certainly will be strong dynamics. 

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Only trouble with backing the winds with the low developing farther to the south is it inch increase the chances of a stable layer messing things up to the north of that low.  Heck, the Nam already has the surface RH near 100 percent on Wednesday which opens the possibility of fog messing things up for us here in the DC area though I'm not sure that would stop gusts from reaching the ground. I do think it would hurt our chances of getting tornadoes due to stability issues but you're more a severe weather guy than I am.  There certainly will be strong dynamics. 

I'll go ahead and guess we get a really gusty line of showers and storms - I will remain pessimistic on the tornado threat until we have a 5% tor risk on that morning.

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I said I'd come back when the severe weather does :) Still not touching the snow threads, though.

Only trouble with backing the winds with the low developing farther to the south is it inch increase the chances of a stable layer messing things up to the north of that low.  Heck, the Nam already has the surface RH near 100 percent on Wednesday which opens the possibility of fog messing things up for us here in the DC area though I'm not sure that would stop gusts from reaching the ground. I do think it would hurt our chances of getting tornadoes due to stability issues but you're more a severe weather guy than I am.  There certainly will be strong dynamics. 

I agree RE: the risks with bringing the secondary low into the equation. At the moment, I have to mostly disregard the NAM solution and count it as a risk rather than anything substantial. The main thing to watch will be a squall line along the front, which should have a ton of lift and should be able to overcome a weak to even moderate strength stable layer. I don't think tornadoes will be in play across the Mid-Atlantic, but it could be a threat in far southern VA into the Carolinas IF better instability can work in.

While not as much of a risk, there could be timing issues for the eastern areas if the slower solutions verify (making it a more evening/overnight event).

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A widespread strong to severe wind event appears to be unfolding over the eastern half of the U.S. Tuesday into Wednesday, with isolated tornadoes also a threat, which is mostly across parts of the Southeast. The Mid-Atlantic has some opportunity for both on Wednesday, with the main threat obviously being a line of strong to severe winds.

We will be battling marginal lapse rates and pre-frontal clouds/rain, as we normally do in these early year setups. Very strong winds aloft (50-60 kt jet at 925mb!) suggests any sort of convection will bring down strong to severe level winds. With the strong forcing associated with the cold front, I don't see much of a problem getting those winds to the surface. The only issue would be if a stable layer at the surface can linger ahead of the front, but that appears to be just a minor problem as the lift from the front should overcome the stable layer (if there is indeed a stable layer).

With dewpoints climbing into the lower 60s ahead of the front, we should be able to see a fairly strong frontal passage with widespread strong to severe winds. The main thing I'm watching now is the potential of a secondary low formation, which the NAM has (though that can't be relied upon at this point). The Euro also develops a secondary low, but it comes later and further north than the NAM. If this secondary low develops before the front comes through, and if it's far enough south, it will be able to back the winds more at the surface and would provide a greater risk for tornadoes in the Mid-Atlantic.

attachicon.gif20130127_GFSdewpoints.png

attachicon.gif20130127_GFSwinds925mb.png

 

 

lol...shows up out of nowhere after boycotting the forum all winter only to bust badly...welcome!

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