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Short-Term Severe/Flooding Discussion


Quincy
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1 hour ago, nrgjeff said:

12Z model suite is friendly to the SPC Day 5 valid Sunday. Low CAPE high shear severe is not limited to Dixie Alley at night. Recent studies show such events as frequent or even more frequent in the Plains all times of day. Sunday looks like robust speed shear with adequate directional shear. Dewpoints are just-in-time, a concern in spring but just the way it goes in winter. Figure helecity will be locally higher on the lifting warm front. If it is not going to snow for Christmas, why not severe?

I could give you several societal reasons, one of which being we had enough folks die last 12/26 in D/FW from post-Christmas tornadoes. Such desires tend to wane in a hurry after an event like that happens in your backyard. Luckily this upcoming event will likely only feature a few strong wind gusts in my coverage area (Texas). 

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Might be mainly straight line winds from Texas to Kansas, vs tornadoes. Farther the low tracks north, the less direct it can tap the Gulf. Instability looks even lower now. Plenty of kinematics will be available for wind though. 

Now I figure something got lost in translation, text only over the Internet. You are not questioning my enthusiasm for severe weather? Would be pretty ironic from the Texas Storm Chasers, lol!

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We all want storms/blizzards/interesting weather, that's why we are here in the first place. That doesn't mean we want to see it cause harm to anyone or their property.

 

But that is the nature of the weather and there's nothing we can do about it except raise awareness and track it.

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  • 1 month later...

Louisiana tornado situation is getting more serious today (Tue Feb 7) with confirmed tornadoes either by debris sig or observation. Gulf Coast boundary is pronounced as it lifts north bringing higher theta-e air, and low level winds are the right direction considering what is going on upstairs. At first glance 700/850 mb appear veered off, but not so relative to other levels. Winds at 200/500 are from the northwest and west-northwest; so, the whole profile has a lot of turning. Surface to upper levels is a classic hodograph, just rotated about 30-45 degrees. 

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  • 1 month later...

Thursday PM is gradually becoming more interesting with respect to a localized severe threat across the southeastern KS/southwestern MO/northeastern OK/northern AR vicinity. 

The large scale pattern is not particularly interesting, but a wave of low pressure is modeled to develop over eastern Kansas Thursday afternoon and drop southeast into the Ozarks Thursday evening. The more conservative 12z EC and 00z GFS show a plume of modest instability, on the order of 500-1000 J/kg MLCAPE, streaming into southeastern Kansas by 00z Friday amidst mid to upper 50s dew-points and 40-50 knots of 0-6km shear. At face value, this supports at least a localized severe threat. The usually more bullish NAM brings dews into the lower 60s in the same area with CAPEs around 2000 J/kg.

Low level winds around south-southwesterly are still favorable given a vertically veering wind profile, as winds in the upper levels veer to WNW/NW Thursday evening. Forecast hodographs in the 0-3km layer become enlarged immediately ahead of the system with an increasing low level jet. A subtle vorticity wave in the progressive flow regime appears to be allowing a wave of low pressure to form along the front. 

With respect to severe, the convective mode is complex, as elevated storms may form just ahead of an effective warm front Thursday afternoon, displaced from more favorable moisture to the south. A cluster of storms may initiate in the vicinity of the surface low shortly after peak heating, with a lack of large scale forcing. The 00z 4km NAM solution drops a broken line of storms into the Ozarks Thursday evening, but this may be overdone due to bloated moisture return/instability. Otherwise the shear profiles are favorable for severe, so if overnight model runs continue the trend of better moisture return, the SPC could introduce a slight risk area in upcoming day 2 convective outlook(s).

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SPC has delineated 5% tornado probabilities for the immediate AR/KS/MO/OK border region, including Joplin, for today. 

Assuming morning convection doesn't destroy the environment, some of the higher end model forecasts for instability (locally 2000+ J/KG) should be realized to about as far north as PPF-SGF. Early day convection could persist and become routed in/near the surface by afternoon/early evening. This has been shown in several consecutive runs of the HRRRX/HRRR and recent 00z NSSL WRF.

A conditional chase day continues, as the terrain and road networks remain favorable for the first few hours of robust storm development, before convection moves into the more hostile Ozarks through the evening. 

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42 minutes ago, Quincy said:

some of the higher end model forecasts for instability (locally 2000+ J/KG) should be realized to about as far north as PPF-SGF. 

NCAR ensemble guidance is rather bullish as well with instability:

image.png

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Elevated WAA thunderstorms are ongoing across southeastern Kansas, feeding from a plume of 1000+ J/kg MUCAPE. It will be interesting to see if this convection leaves an outflow boundary that could influence afternoon storm development, and/or if this convection eventually becomes near-surface based as it spreads east into Missouri. 

image.jpeg

Either way, fairly rapid moisture return is noted with a 10F dew-point increase at JLN over the past two hours. Based on the trajectory of these storms thus far, they should have little if any negative effects to afternoon convective development  

 

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20 minutes ago, Quincy said:

Elevated WAA thunderstorms are ongoing across southeastern Kansas, feeding from a plume of 1000+ J/kg MUCAPE. It will be interesting to see if this convection leaves an outflow boundary that could influence afternoon storm development, and/or if this convection eventually becomes near-surface based as it spreads east into Missouri. 

image.jpeg

Either way, fairly rapid moisture return is noted with a 10F dew-point increase at JLN over the past two hours. Based on the trajectory of these storms thus far, they should have little if any negative effects to afternoon convective development  

 

Pretty small cells, not sure I'd expect an outflow boundary from them unless they congealed into a big mess. 

 

And if that were the case, there wouldn't be much time for the cool side to modify.

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15 minutes ago, Jim Martin said:

Incredible Three Body Scattered Spike on this supercell headed for Springfield.

Definitely looks like Springfield will miss the worst of the storm, with the main part diving hard right to their south.

And the storm is definitely winning the battle versus the weaker storms to the west. 

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