Severe Weather Discussion 2007-12-4

Severe Weather Discussion for October 14, 2007.
Valid: 10/13/2007.

Highlights:

– Active severe weather day expected across western and central Oklahoma on Sunday. Primary threats are damaging winds and large hail, however isolated tornadoes are possible.

– Additional severe thunderstorm chances are possible Wed – Fri. Confidence is low, so will wait another day.

Discussion:

12z/18z models remain about the same with the overall setup. There are two chances that I just caught onto with the 12z runs. The first one is the cold front makes rapid progress southeast during the day and appears to be in northwest Oklahoma by Sunday evening. This seems to be due to the surface low reforming near CDS. The second issue is convective initiation. Models have delay convection until after 00z and hence dark. I see little to no activity in southwest Oklahoma, which may be the prime spot for any development. Even the SREF show no development until after 00z.

Evening surface analysis shows decent moisture confined to the Gulf Coast with some attempt at northward transport. This seems to be slower than earlier thought, but tomorrow morning will tell the tale. Surface heating should be strong as clouds and showers remain limited in the warm sector. Closed low progged to progress slowly across the region with some energy in the base of the trof. This may be what causes the surface low to reform near CDS, resulting in a rapid frontal movement into NW Oklahoma. Despite the moisture concerns, CAPE value should be at least 2000 J/Kg and LIs to -6. Morning models should have a better handle on the expected moisture return.

The main concern is time of convective initiation. At this point the models point to a post sunset initiation. Even when storms do develop the cold front will force a squall line. Storms may develop ahead of the line and these would have a tornado threat. But as already noted, this should be after dark. For now, just going to monitor what happens and see if a chase is possible. I think maybe one or two storms can go mid-afternoon in western Oklahoma as the 500mb jet max punches out across the region. The 00z models should be good.

I think damaging wind potential by itself warrants a moderate, we'll see what SPC does in the morning.

Probabilities:

Risk area for any part of OK/TX (valid: 10/14 Day 1):

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

Chase Status:

Level 2 – Holding at Level 2 right now to evaluate moisture return and cold front movement tomorrow.

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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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