Chase Discussion for April 24, 2007.
Initial Target Area: El Reno to Weatherford
Time: 14:00 – 15:00
Finally getting some of my high resolution stuff back from COD. Despite that the 00z NAM is holding with the dryline in western Oklahoma. While I can't give an exact location, it doesn't make it to OKC and that's what I expected. 00z sounding from FWD showed 200 mb of 10C + moisture and OUN has 150mb worth…very difficult to mix that out unless you have southwest or west winds at 850mb. Now, what we have to deal with is timing of initiation and early morning showers.
A weak subtropical shortwave trof is moving through west Texas this evening and this has resulted in a few supercells near Midland and San Angelo, along with Del Rio. For the most part, SPC's tornado watch for the panhandles was a bust. Oklahoma saw some tornadic activity near Woodward this evening. Said shortwave trof should continue moving northeast but presence of a strong cap should keep surface based convection at bay. Elevated storms are possible as this wave interacts with a strengthening low level jet. This wave should put parts of Oklahoma in NVA Tuesday morning and may help clear out the clouds. Evening obs indicate cirrus has thinned significantly across Oklahoma. Still expect some stratus in the morning and this may make warming up difficult. NAM does warm us to at least 75F with CAPE values approaching 3000 J/Kg. Once again, all this assumes we don't have shower activity in the morning. Wind fields are more than favorable for supercells and the NAM is having
usual problems with helicity.
Timing of convective initiation is still tough. I'm thinking 3pm – 4pm at this point. We'll also have to closely monitor any density boundaries for initiation as the cap should rapidly cool during the afternoon. I do think the NAM is over cooling it as it didn't get it right tonight and probably isn't getting it right tomorrow. The target area is close, so no need to get overly aggressive on leaving. In fact, waiting a little bit may be the best course of action. I really expect the departure time and target location to change as this setup is quite fluid.
Progged wind fields and thermodynamics point towards a significant severe weather event for central and eastern Oklahoma. Models likely do not have a good grasp on how significant this event will be. I expect an enhanced moderate risk in the morning and won't be too shocked at a high. I do think SPC will wait until 16:30z before going to a high, assuming it is necessary.
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