Severe Weather Discussion 2009-7-2

Severe Weather Discussion for October 1, 2009.
Valid: 09/29/2009.

Highlights:

– Severe thunderstorms are likely in Oklahoma Thursday afternoon and
evening. The greatest impact area is eastern Oklahoma, however
central sections may also experience impacts.

Discussion:

Model issues remain and the forecast is still very complex. The
general theme remains the same as a western U.S. trof is expected to
move into the central U.S. on Thursday and close off. Ahead of this
system a warm and very moist airmass will move into Oklahoma, KS/MO by
Thursday morning. Morning lows will be unseasonably warm and little
sun will be necessary to warm up the atmosphere. Wind fields at this
time will be quite favorable for severe thunderstorms and will further
increase in the mid-levels as the upper system approaches. With this
being said, conditions will be supportive of widespread severe
thunderstorms Thursday afternoon and evening across the region. Two
issues remain unresolved this afternoon 1) system speed and 2) morning
convection. I have little control over the latter and I'd think some
activity is likely across the threat area. Depth of convection will
ultimately determine if the full potential of this event is realized.

The former remains a primary topic of discussion among my peer group.
Andy and I spent the better part of the morning arguing about the
speed of the system. I'm in the slower domain and Andy is in the
faster domain. This forecast is centered around an equal potential
for both to occur. Despite which one happens, severe weather impacts
in Oklahoma are likely.

12z NAM is the slowest of the models with the upper system and the GFS
the fastest. From what I can tell of the ECMWF (only have 24 hour
increments) is this model is in the model and the GFS is farthest
east. NAM has the dryline from Osage Co to El Reno to Wichita Falls
at 7pm on Thursday while the GFS is in AR/NE TX with the cold front.
I continue to find the GFS's solution difficult to believe, but will
hold true to all possibilities this far out.

End result is that Thursday will be a dynamic weather day no matter
what model verifies. I do think SPC will go with a moderate risk, the
area will depend on the SREF's and 00z runs.

Probabilities:

Risk area for any part of OK/TX (valid: 09/30 Day 2):

Slight: 100%
Moderate: 90%
High: 0%

Chase Status:

Level 1 – I'm holding it here for another few model runs and see if
the timing differences get resolved.

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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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