Severe Weather Discussion – 2008-10-1

Severe Weather Discussion for May 1, 2008.
Valid: 04/28/2008.

Highlights:

– Severe thunderstorms are possible across central and eastern
Oklahoma on Thursday.

Discussion:

12z models continue prior trends of developing a medium wavelength
trof/closed low in the western U.S. by Thursday afternoon. While
there are questions regarding the evolution of this event, model
severe weather signals are consistent enough to initiate discussions.
A medium-end event appears possible given strong surface heating,
directional/speed shear, and modest deep layer moisture.

Unseasonably deep and cold longwave trof continues over the eastern
U.S. with the resulting Canadian cold front moving through the Gulf.
This will limit moisture return through early Wednesday. Next upper
system moves onshore in the Pacific northwest late Tuesday, with a lee
surface low developing. This will intensify southerly flow across
Oklahoma as moisture attempts to return north. Presence of Canadian
high nearby will result in modified moisture return of dewpoints
around 55F through late Wednesday.

The upper trof approaches the region on Thursday with more robust
moisture return occurring Thursday morning. Model's consistently prog
surface dewpoints in the mid 60s across central/eastern Oklahoma
Thursday afternoon with 850mb dewpoints 12-14C. The dryline is
progged to near I-35 and this appears to be functions of mixing and
the 850mb low lifting into Nebraska, pushing moisture east. While I
do think the dryline will mix into Oklahoma as temperatures will be
warm and moisture initially shallow, I'm not sure it will reach I-35.
This may also be supported by the upper system slowing down, which has
already been noted.

While moisture remains an issue and obviously the EML, confidence does
exist that a medium-end event may occur. I don't think SPC will do a
moderate on the Day 3 product, but a slight risk from northern Texas
into Nebraska/Iowa seems likely. They'll probably highlight a 30%
area from east central Oklahoma into east central Kansas.

Probabilities:

Risk area for any part of OK/TX (valid: 04/29, Day 3):

Slight: 100%
Moderate: 40%
High: N/A

Chase Status:

Level 1 – Normal

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About Putnam Reiter

Putnam has been storm chasing since 1990 and is a co-founder of Hook-Echo.com. For his day job, Putnam works in emergency management for information technology.
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