5/13 FCST: OK/KS/TX

[Jeff Snyder]

Well, I check out the latest 0z ETA to see what Wednesday looks like. I then check out Thursday to see if things have changed... WOW...

The 0z ETA off COD has CAPE ~5000 by 18z, and likely peaking near 6000 in the afternoon (ETA breaks out precip, which cools and decreases CAPE) along the eastern part of the OK/KS border. At the same time, very strong low level shear (ETA has 0-3k helicity 250-400+ by 0z) develops north of what looks like some sort of boundary that ETA has from northeast of OKC to Texarkana area. A small area of enhanced mid-level flow approaches the area too by afternoon... With extreme instability (hey, 6000 CAPE is pretty much as high as it gets) and instense low-level shear north of the boundary, Thursday could be quite intense. IF this were to verify, I wouldn't doubt violent tornadoes possible... Of course, storm mode is yet to be seen, as is whether or not the mid-level flow can prevent the storms from going HP right away... Whatever the case, definately very interesting...

 

[Chris C Sanner]

SPC mentions the possibility of a significant severe weather event Thursday and after looking at things, I'm apt to agree with them. If (IF) we can keep these things slow moving (which looks very good right now) this could be a huge day for chasers, but not for whatever towns are hit. If all of this verifies and these storms are discrete, I wouldn't doubt us not seeing a violent tornado (or two) Thursday somewhere.

 

[John Cameron]

Sure looks like the instability will be there! In fact, its the best forecast for instability Ive seen this spring. Not real impressed with the 500/300mb forecasts, but the outlook for multiple shortwaves is optimistic and the trough looks damn good on water vapor. Bring it on! I'm ready! I also like the prospect for discrete, slow moving storms.

disclaimer: since I'm not a chaser, I base my outlooks on forecasts for the Wichita Falls, Texas area (my permanent "target area")

 

[Jason A.C. Brock]

Dont worry John ill send ya some pics. Ill be out tomorrow & the rest of the week as well. Where ill end up who knows.....NC OK looks decent tomorrow & there are alot of good areas Thursay.

 

[Tony Laubach]

The question is.. do I? :wink:

I've got time off this evening to chase the NE Panhandle; then looking at SPC's analysis, I could chase East Kansas Wednesday...

But the big question.. do I chase Thursday, too? Most would say yes; I guess it would all come down to whether or not I could get coverage for work on Friday! I've been doing a lot of that this week, and so far, I've been successful. Looking at the models for Thursday, I was forced to wipe drool from my chin and ponder the thought.. I mean, I am making up hours at work on Saturday, which would be a good time to put up this entire week (I'd end up chasing Mon, Tues, Wed, and Thurs)...

Hmmm... if I can do it, I'll be out there.. this week makes for a nice circle around the Plains...

HOWEVER...IT APPEARS THAT A RATHER SIGNIFICANT SEVERE WEATHER EPISODE WILL OCCUR ON THURSDAY IN PARTS OF KS/OK/TX.

That's just too hard to ignore..

 

[Jason Montano]

Unfortunatley I am in one of those 3 week, five days a week, 3hour a day, intersession classes and skipping a class is not good. Oh well....looks like I am skipping the class on Wed. and Thurs. I like Wed but am real excited about Thursday. Those CAPE values are tremendous, now to figure out best place to setup....

 

[Chris Hayes]

I'm not out there to get in on the fun yet :cry: :cry: :cry: I could POSSIBLY nowcast for someone though. If this thing goes like it could I'll be watching radar anyhow

 

[Jeff Snyder]

I am still at disbelief of the extreme instability that ETA has been forecasting... I mean, even at 12z, it shows CAPEs >4000 across much of the warm/moist sector of OK and TX east of the dryline and south of the cold front... AT 12Z!! Check out http://www.wxcaster2.com/CENTRAL_MESO-ETA_...HSWEAT_48HR.gif

An experimental long-run RUC from http://maps.fsl.noaa.gov also paints CAPEs ~4000 by 12z Thursday, although it has the dryline farther west and the cold front farther north. The amazing thing is that the ETA has been very consistent in showing this extreme instability developing Thursday, so it's not like a single-run fluke.

As has been the case almost the entire year, there is progged to be weak shear. However, depending upon outflow boundaries left behind by Weds. night convection, we could end up with a decent chase day...

 

[Robert Dewey]

Actually looks like a good setup. As Jeff said, shear is not excellent, more on the weaker side, but I do see a slight increase in total shear during the evening hours of the 13th across central OK. If the CAPEs of >4250j/kg are realized, I doubt the weak shear would limit storms too much...

Just an interesting note: I remember several years back, here in MI, temps climbed to just above 100F with Td's hitting 80F in Chicago, and 78F here in Detroit. CAPEs were >6000j/kg that day, with very little shear (unidirectional with 10-15knts through the column)...A weak cold front slammed through the region producing a squall line, with numerous reports of wind damage. I didn't chase that day, but my home was hit with one of the lines of storms, with a wind gust to 90mph, snapping many of the trees in our neighborhood and damaging several houses... My guess is that the extreme CAPE caused a "precip loading" type event, with a significant microburst as the storm core punched down to the SFC.


Robert

 

[Melissa Moon]

I am putting confidence into Thursday.

Right now, looking at the 18z ETA for Thursday, I like the area not too far east of I-35 in N. Oklahoma into S. Kansas. The CAPE is phenominal, and there is a tounge of some somewhat-decent shear there. The winds also seem to be better at this location; it seems like there is a SW component everywhere except this one little patch in N. OK/S. KS where there is a SE component near the surface low. I also like the Td's v T in this area.

My complaint (once again) is the shear. Areas with good shear seem to have the weaker CAPEs and vice versa...maybe the runs closer to the event will produce a nice balance between the two. Also concerned that this high instability will cause everything to go up at once, and everything will choke everything.

I think something will happen, but I really cannot put my finger on where with full confidence. I'll wait to do that until I see what Wednesday evening/night leaves behind.

 

[Damon Shaw]

Originally posted by Melissa Moon


Also concerned that this high instability will cause everything to go up at once, and everything will choke everything.

I agree with that. While forecast CAPEs are impressive, the 850mb temperatures are expected to cool for much of the Southern Plains on Thursday. Thus, cap will be weaker. Because of the weaker cap and lack of shear, I think it will be multicells with a few HP supercells.

Overall, I like the setup on Wednesday better. But, if an MCS develops out of Kansas and into Northern Oklahoma late Wednesday/early Thursday, then lays down a nice outflow boundary further south, that could change things.

 

[Jeff Snyder]

I don't see how high instability can cause more storms to form. The number of storms that form is more due to the opposing combinations of forcing and capping. If there is too much forcing for the given cap strength, you'll get plenty 'o storms; if there isn't enough forcing for a given cap strength, you'll get a big 'o bust. In either case, you still need a source for surface convergence in order to initiate an updraft. There can be 10000 j/kg CAPE, but the balance between forcing and cap strength (or CIN I suppose) is what usually dictates surface-based convective coverage. For the example of high forcing, low capping, the degree of instability will just give you a clue about whether you'll have a line of showers or a raging bow echo. Likewise, for the too little forcing for the given cap strength, it doesn't matter if you have 100 j/kg CAPE or 5000 j/kg, because that surface parcel just isn't going reach the LFC. High CAPE will likely cause high updraft acceleration, but I don't see how the presence of strong instability will initiate new convection by itself...

P.S. -- Just remember, you don't need a decent cap to keep supercell discrete.... The May 3rd, 1999 outbreak in Oklahoma was characterized by only a weak cap...

 

[Shane Adams]

There's hope in SW OK, because of a nice fetch of low-20s temps at h85. There will be weak shear, but with CAPE approaching well over 4000j/kg in that area, I think weaker shear can be overcome....and with those 20s temps at h85, they'll be a much better chance at isolated storms IMO. I just keep thinking of the Jarrell, TX storm.....there wasn't much for chear that day at all, with the storm propagating southwestward down a boundary and virtually standing still. Since it's obvious 2004 can't juxtapose any decent parameters, I'll take extreme instability with weak shear over better shear and less CAPE any day.

But we'll just have to wait and see......I've still got a chase to forecast tomorrow.

 

[Blake Naftel]

Brief post as I must tackle numerous homework assignments tonight; and get things handed in early before departing for Norman Wednesday afternoon. Plan to chase the RRV (Red River Valley) region Thursday, as my fear is that a massive MCS will screw up the mesoscale environment across OK Wednesday night; pushing the foci (there's my Roger Edwards'esque term for the evening) of dynamics along/and south of the Red River. IMO; Thursday will be a N. Texas day... but I could be wrong.

0Z 48hr ETA (NCAR is down; using Earl Barker's modeling below)...

http://www.wxcaster2.com/CENTRAL_ETA_1000-...PRPTHK_48HR.gif

... would suggest points along and east of I-35 (Jungles... whoohooo, get your chainsaws ready) for Thursday... but that pesky MCS is not being factored in (perhaps the YUC (RUC) will pick up on this. We shall see.

Looking forward to chase potential Thursday; and Rocky's party in Piedmont Saturday. I'll be sure to bring some chaser jackassery video.

Enjoy your precious isodrosotherms.

..Blake..

 

[John Cameron]

A quick snapshot of tomorrow afternoon suggests the models are in lock-step with impressive instability. I have yet to see any evidence of workable shear (in North Texas). We may have to hang our hats on an
approaching outflow boundry. Forecast soundings aren't offering anything resembling a cap either. The best chase scenario for the SPS area is if the front pushed in and dropped anchor.

disclaimer: since I'm not a chaser, I base my outlooks on forecasts for the Wichita Falls, Texas area (my permanent "target area")