Chase Discussion for May 5, 2007.
Target Area: Elk City/Sayre
Departure Time: 14:00 CDT
Current Risk Area: Moderate
00z NAM brings back some major deja vu for Saturday, reference the 23rd/24th. First, a lone supercell developed in the Texas panhandle this evening and moved into Northwest Oklahoma. This storm split a few times and produced at least two tornadoes. Very similar to what happened on April 23rd, other than those storms developed in Oklahoma.
Now, the 00z NAM wants to develop a squall line along the dryline Saturday morning and move it across the region. It fails to develop convection behind this line tomorrow afternoon/evening. This continues to complicate matters given prior issues this year. I'm a big on model trends and this is one I don't like, because it would greatly reduce the threat tomorrow. I'm not completely sold on this solution for a few reasons: 1) no energy moving across the dryline to light it up from Kansas to Mexico, which the NAM does and 2) the 00z NAM under initialized 700mb temps. If this is carried through to later forecasts, then it may explain how the NAM can develop a 600 mile long squall line with seemingly little support. It should be noted that the cap strength is much stronger than the 24th. Midland sounding had 12C 700mb temps at 00z, that air is moving this way.
Point sounding for Clinton yields something I wouldn't expect given NAM precip fields, it does not saturate the environment. Another consideration is that the NAM has 0.01 to 0.10 QPF, any thing that develops will produce much more than 0.10. Therefore, I'm (at the risk of insanity) going to use my prior reasoning from 1.5 weeks ago. I think the NAM is struggling with the deep layer tropical moisture and is convinced there has to be convection. It appears that once the convective parameterization turns on, it goes to town all the way to Mexico.
Long story short, we're still in the wait and see mode. The forecast sounding for tomorrow afternoon at Clinton is impressive with CAPE values around 4500 J/Kg and ML CAPE 3500 J/Kg. LI -6, EHI 5.5, supercell potential 77%. Some of these numbers are likely to change, but look pretty impressive at this point. The chase is still scheduled and we'll see what happens in the morning. I am happy that as 10pm approaches, all is quiet in western OK/TX.
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