Severe Weather Discussion 2007-4-1

Severe Weather Discussion for February 28, 2007.
Valid: 02/24/2007.

Highlights:

– Severe thunderstorms are possible across north Texas into Kansas Wednesday and potentially into Thursday.

Discussion:

I got so had last night. I'm not sure what to say about my bad forecasting or what went wrong. I'm proud I got the panhandle activity, but nothing develop overnight that was what I predicted. My best guess as to what went wrong is the limited moisture and low daytime temperatures resulted in too little instability. As such, when storms tried to develop on the dryline around midnight they were sheared apart by the 60kt low level jet. James with NWS Norman pointed this out Thursday night and he was right on the money. It is a lesson learned and I'll try to work up an event summary to post on Hook-echo.com.

On to the next event, as it is best to jump back in the saddle after screwing up. I usually would wait until tomorrow before starting these, but it is a good time.

SPC Day 4-8 prog is highlighting severe potential for much of the region (central/east TX/OK/KS on east) for Thursday and Friday. I disagree with the timing as the forecaster believes the upper system will slow and impact the region on Thursday. The mid-level pattern is quite progressive right now and I see no reason for this system to suddenly slow. The 00z ECMWF and prior 3 runs of the GFS agree on the timing of this system; impacting the region on Wednesday. I'll leave the door open in case it slows, but right now I'm not forecasting it. The prior system (the current one) did not slow much.

Powerful closed and progressive low is traversing the region this afternoon. Associated surface low is located in east central Kansas with the dryline bulging into Arkansas. Only a few remaining Mesonet stations in Oklahoma continue to report dewpoints above 50F. The majority of stations are around or below 35F. Dryline line should be out of the state within the next few hours as the low lifts northeast out of the region. A cold front will move through the state tonight, but the air behind it is Pacific origin and little cooling is expected; however, temperatures will be much cooler than experienced the past few days and closer to seasonal norms.

12z GFS 30mb moisture prog shows that moisture gets pushed to the Gulf Coast and about 200 miles off. This isn't too significant and a rouge surface high is not expected to block the Gulf. Once the prior system moves away, moisture return should start. This is expected on Monday along the Gulf Coast. Moisture will not recover much beyond the Gulf Coast as low level flow across the region is weak. By Tuesday the next longwave trof is expected to move onto the western coast. This one is expected to remain progressive and move into the region on Wednesday. Moisture return will start in earnest on Tuesday as surface and 850mb lows intensify. However, the quick progressive of the upper system will limit the time necessary for moisture return. Current GFS moisture prog shows 55F dewpoints into southern Oklahoma late Wednesday. 12z NAM dewpoint progs at 84 hrs do not match up with the 12z GFS at the same time period. The NAM is much more bullish with moisture return than
the GFS.
At this point I find the GFS moisture prog more consistent, but will watch these differences the next few days.

Incoming system appears to be just as dynamic as the one that is leaving. This would include a 50-60kt 850mb jet and similar speeds at 700mb. Since this got me last night, I'm going to be careful with the severe weather threat. If moisture can increase with decent daytime heating or the system slows down till Thursday, then the severe weather threat will increase. For now the likely scenario is a high-end slight risk for eastern Oklahoma/Texas.

Probabilities:

Continuation of SPC highlighting Wednesday in Day 4-8 Outlook.

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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