Severe Weather Discussion 2007-9-4

Severe Weather Discussion for May 5 – 7, 2007.
Valid: 05/05/2007.

*Significant Severe Weather Event Today*

Highlights:

– Outbreak of tornadoes and severe thunderstorms appears likely today, especially in Kansas and Nebraska. Across western Oklahoma activity should be more isolated, but still very intense. Primary threats with any activity will be strong tornadoes, destructive hail, and damaging winds.

– Active severe weather day is possible on Sunday from central Texas into Kansas.

– Severe thunderstorms are possible in central Texas on Monday.

Discussion:

Little time for a discussion today as my main focus has been on the developing weather situation for today. SPC has a PDS tornado watch up for northern KS/southern Nebraska and this is certainly a good idea. The high risk is also well placed.

The threat for Oklahoma is conditional once again today. The atmosphere is in a very similar condition today as yesterday. This means that CAPE values will again approach 5000 J/Kg with LIs to -10. This extreme instability, when combined with decent speed/directional shear will allow any storm that develops to rapidly form into a supercell. The main question is IF storms will develop and then how many. My thinking is that two, maybe three storms will form in western Oklahoma later today. OUN has a moderate risk for much of northwest Oklahoma and this looks good. I think it should come farther south, but not gonna worry about it.

Storms should move northeast through the region tonight as the dryline retreats to the west. Storms may form late tonight on the dryline as a shortwave trof impinges on this feature and the very unstable atmosphere. Even though temperatures will be at min values for the day, CAPE values should still be 3500 J/Kg, more than enough for intense activity. Question again is IF storms can develop.

Sunday has huge potential if there isn't widespread overnight convection. Models are worthless here as none of them have the current environment correct. Conditions will be similar with the dryline farther east into Oklahoma. A chase is possible on Sunday, depending on what happens today.

Monday looks to be in central Texas and SPC Day 3 seems to have a good handle on it.

A heavy rain event appears possible across parts of the region, but model disagreement makes that tough to forecast.

Both Day 1 and 2 risk areas are very conditional on activity in the morning and the prior evening.

Probabilities:

Risk area for any part of OK/TX (valid: 05/06 Day 1, Day 2):

Slight: 100%, 100%
Moderate: 75%, 35%
High: 5%, 0%

Chase Status:

Level 4 – Heading to Arnett at 13:00.

For more information, weather news, weather blog, and chase summaries go to http://www.hook-echo.com.

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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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