Severe Weather Discussion – 2008-7-3

Severe Weather Discussion for March 31, 2008 and April 2-3, 2008.
Valid: 03/31/2008.

Highlights:

– Active severe weather day will continue for eastern Texas and
southeast Oklahoma eastward into LA/AR. Primary threats are
tornadoes, destructive hail, and damaging winds.

– Severe thunderstorms are possible in the Texas/OK Panhandles on Wednesday.

– Severe thunderstorms are possible across north Texas and much of
Oklahoma on Thursday.

Discussion:

Crazy night last night with much of the sensible weather unexpected.
The Edmond tornado has been rated an EF-1 with a path length of 3/10
of a mile and width of 50 to 100 yards.

Numerous severe thunderstorms, some capable of producing tornadoes,
continue across eastern parts of OK/TX into AR/LA this afternoon.
Refer to SPC watches and local WFO warnings for nowcast information.

A cold front will push through the region late tonight into Tuesday,
with parts of Oklahoma already experiencing FROPA. 12z NAM/GFS are in
decent agreement on pushing the front to south Texas by late Tuesday
where it stalls as the 1035mb surface high slides east across IL/OH.
This would fit the unamplified 500mb pattern and prevent Gulf
penetration. The models are similar on surface depictions through 48
hours with both these models having the 1016mb line west of Houston
through Wednesday morning. By Wednesday afternoon the 1016mb line
shifts east of Houston and deep layer moisture starts to return north.
GFS is more robust than the NAM and this is probably the correct
solution. The past few days are adequate proof of moisture content.
SPC has a slight risk up for the Texas panhandle and frankly I haven't
spent much time looking at data. This outlook makes since given
persistent southwesterly flow aloft overtopping an increasingly moist
boundary layer. GFS 850mb dewpoints are 10C by 00z Thursday with
MLCAPES approaching 1000 J/Kg in parts of the risk area. This should
be sufficient for isolated severe thunderstorms as the 30-40kt LLJ
increases.

Attention then turns to Thursday which has multiple possibilities,
depending on which model you pick. The NAM is fastest of the bunch
with the upper system through the state by 00z Friday. The GFS is
somewhat slower, favoring severe thunderstorms in eastern Oklahoma.
The ECMWF is even slower favoring a western Oklahoma event. All three
of these models are staying put on their respective forecasts, making
this a very low confidence forecast. I think moisture return will be
quite robust and if either the GFS or ECMWF verifies, another active
severe weather day is likely on Thursday. My probabilities reflect
the uncertainty in my thinking and the fact that I've only had 5 hours
of sleep, if you'd call it that. Discussions will continue.

The chase level is reset to Level 1 given nothing through Wednesday.
I anticipate raising the level again on Tuesday.

It should be noted that the ECMWF continues an unseasonably active
pattern for the next 7 days.

Probabilities:

Risk area for any part of OK/TX (valid: 04/01 Day 2, Day 3):

Slight: 75%, 75%
Moderate: 0%, 0%
High: 0%, 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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