Severe Weather Discussion 2007-7-2

Severe Weather Discussion for April 12 and 13, 2007.
Valid: 04/11/2007.

Highlights:

– Isolated severe thunderstorms are possible in west Texas into southwest Oklahoma. Primary threats are large hail and damagin winds.

– Active severe weather day is expected on Friday across much of eastern Texas into southeast Oklahoma. Tornadoes, destructive hail, and damaging winds are all possible.

– Across the remainder of Oklahoma hail to nickel size and excessive rainfall will be the primary threats on Friday. Flash flooding is possible.

Discussion:

Oh boy yesterday was fun, nice long track supercell moved through southern Oklahoma. One of the better looking "pork chop" structures I've seen in Oklahoma this year. No confirmed tornado reports, but I wouldn't be surprised if it did it once.

Thursday's outlook continues to be the same and I'm not going to rehash the meteorological setup for it. SPC Day 2 has a slight risk up for west Texas into southwest Oklahoma and this looks good.

Friday continues to look very interesting and somewhat prototypical for Texas. The threat for Oklahoma seems to have decreased, but I'm not going to bet the farm yet. Several items will have to be resolved before the threat area can be nailed down.

00z ECMWF/12z NAM are in good agreement, GFS is booted yet again. Latest progs do agree that this system will take a southern route, which will remove much of Oklahoma from the significant severe threat. Tough call as to how much of southeast Oklahoma will be affected on Friday. This is due to the expected warm front position. Models agree that the warm front will struggle to move north on Thursday and will likely stall early Friday as widespread convection develops to the north. Given recent cold air intrusions and cool ground, this scenario makes sense.

Texas continues to be the hot spot for this event with areas east of I-35 under the gun. Models displaying usual biases here and I'm not going to bite onto what they're doing. Wind fields look good and if the cap can hold, discrete supercells are likely Friday afternoon. Cloud cover may be an issue as April sun still isn't good at burning off stratus. Situation certainly has the potential to be significant with an outbreak of severe thunderstorms across this area.

Of equal if not greater concern is the excessive rain threat for Oklahoma. 12z NAM cranks out 2-3 inches of rain across the state through Saturday. There is certainly potential for more rain than this since Texas will be capped. If this is truly the case, flooding may be possible. Flash Flood Guidance values are still moderate across the region and especially in southeast Oklahoma. However, it won't take much rain to bring those numbers down.

OUN talked about snow for parts of Oklahoma late Friday into Saturday. Southern track of system and cool air tap certainly lends credibility to this potential. However, time of year should negate it hanging around long if at all.

I think Friday clearly warrants a moderate risk on the Day 2. My area is College Station to Ardmore and east to LA. I'd correlate that with a 10% hatched area. For now I think this is out of our chase area and will keep the chase status at normal.

Probabilities:

Risk area for any part of OK/TX (valid: 04/12 Day 1, Day 2):

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

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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