3/7/06 FCST: Central / Southern Plains

This setup has bust written all over it. The cirrus deck has persisted longer over Oklahoma/Kansas than I anticipated. More cirrus have developed over NW Oklahoma/SW Kansas in the past couple hours ahead of the vort max currently approaching Southwest Kansas. Speaking of which that vort max will be just east of the target region in the next few hours, meaning subsidence will actually be occuring there at peak heating.

Surface winds have been veering ahead of the dryline over the past few hours over Western Oklahoma and there is a lot of dry air mixing in with the moist axis. 850 tmps should reach around 16 or 17C which would support convective temps in the lower to middile 80s. Current surface temps are struggling to reach the middle 70s with the cirrus shield over Northern OK/Souther Kansas. There needs to be a strong forcing mechanism to break the cap, and there doesn't appear to be one. Surface heating and forcing fromt the dryline won't be enough. Storms may still fire after dark with the low level jet, but there won't be anything to chase during daylight.

March 7 = bust

I sure hope this isn't a sign for what's to come for the rest of the season..
 
My thoughts for today are as follows. The main area will be focused in north western OK to south central KS along a narrow band of higher instabilities and cape which appears to be capped most of the day under subsident DNVA. However approaching 0Z (perhaps as early as 21z) this inhibition may be breached near the intersection of the dryline / low interface by a small approaching mid level wave which may be just enough to break out precipitation. This is conditional IMO. If it does go however I think there is a chance for decent severe with hail, wind, tornadoes. At this point I'd probably go with Slight and maybe a 5% chance of torns. Unfortunately as I say this may be at / near the approach of dark.

I'm stuck at home next two days and can't chase. For you locals though it might be worth keeping an eye on today.
 
I'm finding it interesting that winds are backing in extreme western OK. If you look north of I40 long the OK/TX panhandle border, you'll see that winds are even out of the SSE (at places like Arnett and Camargo). There has to be at least moderate surface convergence right along the OK/TX border given this recent development. Personally, I hold initiation at 20-30%, with with a >90% severe probability given intiation. Strong pressure falls continue to statewide, and Tds are "okay" for March. I still think large hail and damaging winds are the main threats.
 
Latest Mesonet observations show a subtle convergence line developing S and SW of the OKC region, and the clear air mode radar shows some coherent roll structures oriented roughly N-S in Grady and Canadian counties. Dewpoints are creeping into the lower 60's in SC OK, but the dryline is going to have to get moving in order to make something happen. Currently socked in with crap at OUN and no clearing in sight. FWIW, the most recent RUC appears to break out some scattered precip in the I-40/I-44 corridor, but not until right around sunset.
 
I don't know, Jim ... this one could easily still go either way, imo ... vis sat loop appears to show a trend in weakening that cirrus shield. Boundary layer moisture remains along a very narrow axis, but this was anticipated. RUC has been fairly consistent in precip over the same areas by 21-0z ... I agree that there is not a strong mechanism in place as far as forcing is concerned (hence not much confidence), but just feel like this day is still do-able. Looks like I'm definitely in the minority though-
 
Although the cirrus shield is present, we also have to remember one more thing... the CAPE is already present as well. So... although there is currently less heating and subsequently less CAPE, it's not going to take much more than 1000 j/kg to make a supercell capable of producing tornadoes in this kind of a shear situation. The late timing is still a problem, but I wouldn't get too downhearted about a bust day today strictly based on the cirrus and slightly cooler temperatures.

The boundaries are strong and convergence should be enough to get initialization. With enough CAPE, shear, and helicity present, who could really ask for more???
 
Just chiming in to say that I don't think the moisture is shallow, particularly for this early in the season. the FWD/DFW sounding was a little disappointing, but other soundings over TX (particularly se TX) show a ~200mb deep moist layer, which is impressive. The 17z LMN sounding shows a 125mb moist layer, which I'll take for March. Speaking of the 17z LMN sounding, 260 j/kg CINH remains, which is disturbing. Of course, high T and Tds to the west probably means that the cap is weaker than what the LMN suggests. Awesome low-level shear profile, however, with 50kts near 800mb yielding 350-400 0-3k SRH
 
Looking at the latest SPC outlook, they don't seem confident that tornadic activity would happen if there is initiation. This one is 50-50 right now, as the placing of everything seems a little off right now and the cap is still strong. If that wave the SPC is talking about in the latest outlook would come two hours earlier, I'd say game on.

If you are within 40 miles and need some early season chasing, go for it. I'm still thinking a tornado or two is possible (the first event usually seems more favorable in this scenario to produce an isolated tornado than not to, based off of observations in the past 5-7 years).

It's clearing a little up here in Manhattan, so I think there is still hope in the target area.
 
There has been a marked decrease along a line from Guthrie OK to Holton KS. The general area over Enid/Wichita has also seemed to weaken some. With new cloud development right along the 500mb Vorticity lobe.
 
Probably one of those situations Mike where it can go either way. Sometimes when we chase we just have to roll the dice. If your there and it breaks out your rewarded, if not -- Oh well - that's the breaks.

I agree with what others mentioned about the cirrus. Briefly looked at vis sat and thought I saw some.

I may look a bit deeper into other things to see if there is any better potential - probably one of those iffy 'March' chases and they always burn me.
 
Just checked RUC and even though it is showing precip it isn't showing convective precip breaking out at all. This implies IMO the cap won't break and anything will remain elevated.

Edit: Also RUC clouds are forecast ice (cirrus?) above 18K and also supercooled in one small spot just insided eastern TX panhandle and center of KS/OK border right at 0Z.

TPI (Thunderstorm Potential Index) seems to be pretty high throughout target area OK/KS.
 
Originally posted by Bill Tabor
Just checked RUC and even though it is showing precip it isn't showing convective precip breaking out at all. This implies IMO the cap won't break and anything will remain elevated.

Edit: Also RUC clouds are forecast ice (cirrus?) above 18K and also supercooled in one small spot just insided eastern TX panhandle and center of KS/OK border right at 0Z.
Click to expand...

The RUC does show convective precip breaking out near ICT by 0z.
http://www.emc.ncep.noaa.gov/mmb/rucsvrfcst/

and here: http://weather.cod.edu/forecast/RUC/SP/ruc...P_0_cprec_6.gif

Of course the RUC shows almost 1/10 of an inch near Saddle Mountain, OK right now which isn't occuring.

EDIT: After doing some comparsion it looks like the UCAR convective precip is based on the color shading not the lines.
 
The ongoing attack of the cirrus machine is really screwing up even observing from an internet perspective what transpires today. Pity. I wish someone could flip the OFF switch for this stuff...

Visible satellite currently shows clumping of lines of cu from Comanche County OK northeastwards through Oklahoma County OK. This seems to correspond with where the cirrus has managed to erode sufficiently to allow heating and insolation and roughly where temps have managed to climb into the 80s giving us obs on the order of 80/57, 79/57 etc, and where there appears to be some weak surface wind convergence.

For fun - supercell composite's up to 10 on the OK/KS border now.

Karen
 
Well, I will also note that SPC mesoanalysis also shows a small area of -50 cinh in south central OK. There is some moisture convergence in this area but it does not appear to be near the convergent dryline and will probably be south of the later wave influence. Various severe parameters are increasing across thi s area and much of OK - perhaps convective heating.......

That said, I'm stuck at home so (sorry) I don't want it to go and so will slap on my mental convective shield. :lol:
 
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