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Severe Weather Threat in Dixie Alley/OV Feb 27 - Mar 1


Fred Gossage

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Euro 6 hour rainfall panels suggests something has already popped between TUL and ICT by 18Z (Noon), and storms are ongoing in Missouri already by 0Z, and between 0Z and 6Z (tomorrow evening) what appears to be linear storms has already broken out about as far South as Waco. By 18Z Monday rainfall almost an inch or more has occured in all but far Eastern Kentucky, and in Southern Ohio. Its PPV. No images.

CAPE is >1000 J/Kg (I assume surface based) from Northern Oklahoma to Central Missouri by 18Z tomorrow, per the Euro, CAPE is below 500J/Kg everywhere after 12Z Monday morning.

A forecast skew T in Missouri at 0Z tomorrow afternoon/evening at 37.25N and 93.3W shows over 800J/Kg CAPE, TT of 54, helicity over 400 J/Kg. The AccuWx plot doesn't give the LFC, its doesn't looks super low, closer to 800 mb than 850 mb.

Just throwing out the Euro would seem to support chaseable storms before dark SE Kansas, NE Oklahoma and parts of Missouri, although I realize, despite never chasing, getting into hillier and more tree covered terrain makes chasing harder.

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Man, this would be a much better chase opportunity if it was daylight. That's pretty good terrain.

Sorry to reply to myself, but I'm getting some indications that this event could wind up being closer to daybreak Monday morning. PAH conference call seems to be indicating that it could be daylight for central/east portions of the PAH forecast area. Also looks like my local forecast (Perryville, MO) has shifted timing wording towards Monday time period rather than Sunday night.

We're going to need to watch this event closely to see exact timings.

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New GFS looks very squirrelly. Has weakened the overall system substantially versus previous runs and has a strange looking farther south, weaker secondary low plodding east through the TN valley into Monday. Neither run looks much like the 00Z ECMWF, although the NAM certainly maintains a much stronger looking system which is more like the ECMWF, although the timing is slower. At 00Z Tue the 12Z GFS has a 994 mb low just east of Downeast ME, a secondary 1004 mb low over central VA, with a weird looking positively tilted surface trough SW out of it into far SE MS. At the same time, the 00Z ECMWF had a well organized "double barrel" 993 over upstate NY/W PA with a good cold front down into GA/FL Panhandle. The NAM has a 998 mb surface low over KHTS with a front extending S into AL. The upper systems are also light years apart, GFS is way weaker than either the NAM or ECMWF. I love it when the model spread increases the closer to an event one gets.

Anyway, the ECMWF seems to be more consistent, although its ensemble mean would seem to allow for a somewhat weaker solution than its op run shows. Of the 12Z models in so far, I would lean right now towards a somewhat faster version of the NAM - will be interested to see the 12Z ECMWF.

The 18Z NAM and 12Z ECMWF have trended towards the weaker solution, which showed up just as the system moved onshore.

Still not sure how this all will effect severe weather potential, hopefully 0Z runs will clear things out a little.

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The 18Z NAM and 12Z ECMWF have trended towards the weaker solution, which showed up just as the system moved onshore.

Still not sure how this all will effect severe weather potential, hopefully 0Z runs will clear things out a little.

The weaker solution, IMO, would only increase the tornado threat, as it would likely be accompanied by lesser linear forcing.

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The 18Z NAM and 12Z ECMWF have trended towards the weaker solution, which showed up just as the system moved onshore.

Still not sure how this all will effect severe weather potential, hopefully 0Z runs will clear things out a little.

The 18Z GFS trended a bit strongerthan the 12Z - and IMO the ECMWF is still quite a bit stronger than the GFS and only trended a bit weaker. It still has a 998 mb surface low over SE MO at 12Z Monday in comparison to the 18Z GFS which has a somewhat weaker upper system than the EC and a 1004 mb low over NE AR. My guess is it will end up in the middle - stronger than the GFS has been showing the last few runs but not quite as strong as the ECMWF.

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The 18Z GFS trended a bit strongerthan the 12Z - and IMO the ECMWF is still quite a bit stronger than the GFS and only trended a bit weaker. It still has a 998 mb surface low over SE MO at 12Z Monday in comparison to the 18Z GFS which has a somewhat weaker upper system than the EC and a 1004 mb low over NE AR. My guess is it will end up in the middle - stronger than the GFS has been showing the last few runs but not quite as strong as the ECMWF.

I agree -- the middle road is probably the best way to go.

The weaker solution, IMO, would only increase the tornado threat, as it would likely be accompanied by lesser linear forcing.

While there would be lesser linear forcing, it might also mean a weaker surface reflection, and less backing at the surface. Thus my uncertainty.

Although the Euro solution verbatim keeps the surface reflection intact and would imply a significant threat to the Ohio Valley in the predawn hours.

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I agree -- the middle road is probably the best way to go.

While there would be lesser linear forcing, it might also mean a weaker surface reflection, and less backing at the surface. Thus my uncertainty.

Although the Euro solution verbatim keeps the surface reflection intact and would imply a significant threat to the Ohio Valley in the predawn hours.

With the winds aloft WSWrly, a slightly veered sfc flow would still be favorable for strong tornadoes. The GFS, the weakest reflection, still has incredible low-level shear and large, looping hodos with SSW sfc winds...

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Just pushed out a new graphical severe weather threat as of 23Z, looking at NE OK, W. AR, and SW MO as the highest threat with potential for F1/F2 Tornadoes. Again this is my initial outputs on my Smartmodel.

http://smartwxmodel.net

If this is legit, you should post some verification statistics or something similar in the long-run. I'm interested to see how accurate your algorithm is.

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