2011-11-07 FCST: N. TX, SW OK

[Bill Hark]

Monday is a rather impressive set up especially for Novemberwith that approaching trough. I woulddefinitely chase if I lived in the area. I don’t, thus take my forecast with agrain of salt. Both the NAM and GFS (00Z init) show 40 increasing to 50,southwesterly 500 mb flow across southwestern Oklahoma and North Central Texas.There is 60 kt flow just to the west. Ireally like the NAM showing southwesterly 850 mb winds that shift to the southby 00Z and increasing in strength. Thereis even a small area of southeasterly 850 mb winds. Despite my experience withthe Ada tornado last May, I prefer south or southeasterly 850 mb winds. There willbe backed surface winds. Both models show60 degree dewpoints and the Nam shows modest CAPE up to 1500 near the river anda nice area of SRH 200-300. Looking at predicted 700 mb temps, cap shouldn’t bean issue. My biggest concerns arepossible early and widespread precipitation, transition to linear mode and theGFS showing the 850 winds becoming all southwesterly by 00Z. The target area covers places with poor roadnetwork and that pesky Red River and tributary. Right now, I would initially target Hollis, Oklahoma. There are decentroads going out of the town including a nearby river crossing to the south.

Bill Hark

 

[Mike Johnston]

Yea, looking at the RUC, it shows fairly widespread precip might hold on for a good part of the day, even though the convective outlook discussion suggests the precip moving out of the target area to the northeast. Some sunshine/daytime heating will probably be the key for sufficient instability. For this simple reason, and considering the orientation of the surface front, I would shade the target just a bit to the south - say in a corridor from Vernon, TX to Wichita Falls. This area should be on the nose of the low level jet and just out ahead of a dryline bulge (although this is conditional on the latitude of where the surface low ultimately sets up, which seems a bit uncertain.)

 

[Mike Johnston]

Nice call on your Hollis target, Bill. I think the hook on the first tornadic cell was maybe 5 or 10 miles from Hollis when it was initially warned.

Now, I don't see any reason why these supercells won't persist for a few more hours. Height falls starting to spread in from the west, and the low-level jet is out of the due south through central Oklahoma. Also, 0-1km helicity readings have been trending higher. Just enough warming today to create an unstable environment for a very strong November setup. In particular, that cell in northwest Comanche Co., OK has quite a classic look to it. Hope some chasers were out today.