5/13/08 FCST: OK / TX / KS/ AR/ MO

[Ilya Neyman]

High moisture, high cape, high instability and good speed and directional shear all point to active severe event. Sure the low level flow's been stronger, but relative to the significant upper winds it may balance out. Initiation looks pretty legit. now too. Prelim. target: CNTRL OK, expanding east during the evening. OKC metro will be in the region of concern again.

 

[Jeff Piotrowski]

SPC upgrading to moderate at 13Z

The 12Z WRF not much convection at 0Z. But cranks it up after 0Z on the retreating Dl in NW TX.

 

[Jonathan Whitehead]

Yes SPC has upgraded to MDT now.
Sitting here in Wichita pouring over data. I am likely to just target the area along the I-35 corridor btwn Wichita and OKC as I can crash either place. Here in Wichita skies are overcasted from the Gulf stratus that has advected in overnight. I havent really had time to look at everything in great detail due to time constraints but if the cap can hold like SPC and OUN has been discussing, then I dont see why we shouldnt get supercellfest today.

 

[Joey Ketcham]

I'm liking the area along I35 into OKC, I think I will be heading down to Cushing Oklahoma and hang out there for a while. Dewpoints are up to 70 in some areas of Central Oklahoma, 60's in pretty much the rest.

 

[Mike Hollingshead]

Boy does it get old looping the 850mb winds on the spc meso analysis page this year.

http://www.spc.noaa.gov/exper/mesoanalysis/loop.php?sector=1&parm=850mb

Stop blowing the juice east! Might be nice to get those weaker just to slow that down.

12z NAM really moving the dl west in TX by 0z now.
http://www.wxcaster2.com/CENTRAL_ETA_SFC_SLPTMPDPTWINDSLI_12HR.gif

If I had a choice I'd be down into TX west of I35 today, but I'm stuck north and thinking it'd be wisest to stay home and wait for better days. But, I have no patience. I'm starting to wonder if there will be any good enough boundaries east of KC along I70 in MO today. Current satellite loop makes me wonder. Best helicity winds up over there with the LLJ by late afternoon, and some of the deeper moisture may wind up there at this rate. Heading south to KC for now with some serious consideration of going east by the time I get there. Then again I am doubting that one storm leaves a good enough boundary for later. If that's the case will settle on far se KS.

 

[Jeff Snyder]

Not a particularly easy forecast, and Mike noted the veered 850mb flow (the theme this year, apparently) that may give us issues today. Morning soundings show that the rich moisture has advected northward overnight, with the FWD sounding showing a ~150 mb deep moist layer. The EML above the returning moist layer is quite impressive, with the OUN sounding sampling 9.2 C / km 700-500mb lapse rates, including part of a dry-adiabatic layer between 750-550mb. The presence of very steep lapse rates and deep moisture should allow for significant destabilization, excluding possible hindrances of cirrus and top-down moisture depletion caused by dry air advection on the veered flow off the sfc. Speaking of the latter, current profile data from Purcell, OK, show SW flow all the way down to 500m AGL, which is a little concerning to see.

The earlier progs of weak 700mb flow (<20 kts) looks like it won't be as large of an issue, as the latest RUC and NAM progs show >25 kt 700mb flow N of the Red through the evening. In addition, the 12z RUC and NAM runs are forecasting the flow to back behind the dryline by 00z to an easterly direction, which may create convergence problems S of the Red River. Current sfc obs indicate that last night's (00z) NAM run was, predictably, too slow w/ the cold front position this morning; the cold front currently extends along a line from near Lubbock to Childress to Altus to Alva to Salina. Very strong pressure rises (~4.2 mb/3hr) behind the cold front in northwestern OK should ensure that the cold front continues southeastward this morning. That said, as the upper-low continues to approach this afternoon and evening, surface pressure falls in W TX should begin to veer the flow behind the cold front by evening.

I'm still favoring SW through C Oklahoma, particularly since it looks like the triple point is going to be way down near I20 now. Both the RUC and NAM initiate convection from E of Kansas City to San Angelo (and beyond), and a mixed storm mode may dominate given the NNE-SSW orientation of the cold front (w/ 0-6km shear vectors largely to the NE). I'm still not sold on a SE KS target given the NAM consistency in veering the low-level flow ahead of the front up there (though the 12z RUC keeps sfc flow southerly). My thinking is to hang around OUN until early-mid afternoon on the hope that a more specific target will become apparent by that time. The prob of supercells should be relatively greater where the cold front takes a more N-S orientation as such an orientation should allow for a more normal orientation of the deep-layer shear vector to the cold front. FWIW, current sfc obs would argue that would be most in SE KS and adjacent areas of NE OK and SW MO.

 

[Mitchell Daszewski]

Tough forecast for today and just plain bad timing. For those in OK and KS the decision to chase those areas is definitely warranted, but with the chase team in Abiline, I think the best play is sharpening dryline between 0z and 3z this afternoon and evening in central and west Texas.

Morning and early afternoon mid level energy shears out to the northeast over OK and KS during the day leaving a wake of weak mid level winds, subsidence and height rises over the red river right at peak heating. This severely weakens SRH in the area.

However, RUC and NAM are forecasting height falls and developing surface cyclone in west TX later in the day and early evening which begins to sharpen the dryline right near 0z. The RUC at 0z shows a 999Mb surface low south of MAF west of SJT. 13km 15 Hour RUC from fsl continues that trend and low level winds respond with backing flow taking shape through 850Mb and a tightening of the dry line near the triple point. Believe this will be the area of focus from 6PM-8PM time frame as the cap breaks. The RUC is painting 4000 J/kg all along the dry line so storms should become severe quick. Target should be near and around the ABI area.

Good luck to all that chase today.

 

[David Hoadley]

5/13/08 FCST: OK/TX/KS/AR/MO

About to leave Joplin and head down to OKC. My surface based forecast (9AM data) places the center near Yukon and bounded roughly by Alva, Elk City, Altus, Ardmore, McAlester, Cushing, and Alva. Good luck to all out today. - - - Dave Hoadley

 

[Rocky Rascovich]

That's great Dave..! As good of a forecaster as you are, I'll have to clean out my 'fraidy hole. I think tornadic supercells may be limited due to veering winds, surface and aloft. I expect linear storms shortly after initiation close to the farm (5mi. NW of Piedmont). Further east, some discrete cells are more likely as shear profiles are more favourable.

I'll be monitoring conditions into the early PM hours. Today may be one of my last chase days for this season as I start a full time job tomorrow morning.

 

[Bill Tabor]

I'm kind of wondering why SPC had a MD for TX a bit earlier for imminent severe storms. There are storms in TX at the moment, but they appear elevated and sub severe. Mesoanalysis shows significant capping. True..that RUC and NAM erode some of the CINH later perhaps 18z and later in places, but MD seems premature to me. Any thoughts on todays capping and subsidence in TX?

Is anyone able to identify the E/W oriented convergent boundary in mid TX? Is this a pseudo warm front?

I kind of like what I am seeing with the RUC low developing down toward DRT later in the day backing sfc winds.

I agree this could be a tough day to figure out well, and pull a nice tube out of, but I am working on it.

 

[Ryan Pfannkuch]

Preliminary 4 county target area in central/eastern OK:

Payne, Lincoln, Creek, Okfuskee

Currently sitting in Wichita with Ben McMillan and Quintin Erdman...pondering this complex setup. Originally was thinking south of OKC for sure, but I am just not seeing enough of a difference in key parameters along the cold front to justify a big difference between northeast OK and areas farther south along the Red River. The 0z RUC fcst sounding for Cushing shows a very similar CAPE/wind profile compared to areas south/southwest of OKC...and if anything has a little better 0-1km shear setup. In addition, the 13km RUC shows a decent QPF signal across the northeast quadrant of OK for the 0-3z time frame. This, in combination with what appear to be fairly homogenous conditions along much of the frontal boundary, lead me to think that coming from the north just doesn't justify dropping south of I-40 at this time. Will see if later conditions result in a change of heart...

 

[Jason Foster]

Pretty much agreeing with the Central Oklahoma folks attm. I like to look at the Theta-E. Still need to read what it is exactly, but over the years, I tend to see it just as a good indication of "energy". I also wouldn't go east any be under the clouds.

OK, because of the road networks mostly, and I like to start south and move north if necessary.....I'd be at about Waurika. Good North/South options, and I can head east easily when the time is right. With the last two days being quiet, don't think I would have been out of position much on this day.

 

[Mikey Gribble]

I like the Red River area (Ardmore), but the latest RUC shows weak low level winds in this area. I think it may just be out to lunch, so I'll ignore it. I am hoping low level winds will back more along the Red River than points farther North due to the deepening surface low over West Texas.

I haven't looked at much data this morning so I am feeling very under prepared, but it's time to hit the road so I am leaving. If anybody would be available to nowcast in about 2 hours I would appreciate some help. I basically will need some RUC data, vis satellite observations and surface chart info about the time I hit OKC, which will be about 2.5 hours from now. After that I should be fine on data for the rest of the day.

 

[Chris C Sanner]

Sitting here in the hometown of Velma, Oklahoma pouring over data. I really think this might be one of the places to be today with the instabilities being a bit higher. I agree with Mikey as well that I think the RUC is out to lunch on the low level wind fields over the entire area. Also a stronger cap should result in more discrete convection, at least initially, as I'm worried about the linear potential anywhere along the front. My plan is to sit here and monitor the fronts positioning and then hope that the high amounts of instability along with modest wind shear will be enough. The key today IMHO will be getting a deviant mover to get some tornadoes. This year has been tough to forecast for and also tough to get tornadoes, but they have been out there to get. Good luck to everyone, hopefully we can avoid some towns today and the loss of life

 

[Mike Hollingshead]

Does appear there may be some sort of outflow boundary off that ne MO stuff going sw through KC. Can see a fine line on Satellite there and thought I could see it on KC radar via GR3. Not sure it will hang around and be enough, but something to watch.