5/7/2009 FCST OK/TX/KS/MO/IL/AR/KY

[Brendon Lindsey]

Well both models agree with high instability very high, 5000+ , into C. Oklahoma down into Texas. Great moisture 75 DP will be from C. OK down into Texas also. I see a nose on the low pressure in S.C. OK. Skew Ts get upto 95% Supercell Potential. But with the hodographs, I dont really see much curvature. THE BIG PROBLEM is with the cap haha, hopefully the convective temperature can come down 3 or 4 degrees. Lets see what the models do.

Brendon L.

 

[Darrin Rasberry]

Looks like another gamble day that may pay off with a huge beast or a sunny sky (or hail-busted car on a storm that licks its own rear end). 700mb's at ~12 C on the dryline to ~10 C at OKC show a pretty stalwart cap over the whole thing. But the CAPE is excellent, *AND* as a little extra gift so is the shear even at the lower levels (although surface winds could use a kick). I'd chase it if I were you, but I can't risk blowing another hundred coming in from Iowa on a gamble like this. Someday ... someday ... they'll be back in Nebraska.

 

[Michael O'Keeffe]

I'm actually liking E Kansas on Thursday where the LLJ is stronger and backed more to the SSW, which isn't great but with a strong WNW 500mb jet that should create sufficient shear with the SSE surface winds. It also appears the cap will break in E Kansas and several supercells fire by 21z tracking E maybe a bit SE. Helicity will also be pretty good especially south of I70 so if we can get a storm to fire off the dryline and track eastward I think there is a decent shot at tornadoes fairly close to home. I'm in!

 

[Mike Hollingshead]

I'm also starting to like eastern KS or western MO tomorrow. Some of the forecast soundings along that warm front look good enough to me, though low level winds a bit weak, but still.

SZL se of KC 0z

Not sure I buy those kind of dews getting up in there on the 0-5 knot winds most of the time between now and then. They look pretty stuck down south till tomorrow sometime, not that we'd need 70 TDs anyway.

Somewhere south of KC starting to look like a good starting point. I can already feel the headache of going west or east of there. Could see being in MO both the next two days.

 

[Chad Cowan]

Before the 0z runs last night I wrote off this setup as unidirectional because ALL of the previous runs showed the LLJ core scooting off to MO early in the afternoon with westerly 850's over the warm sector in KS. The 0z runs last night showed much better directional shear with SWrly 850s much further west. This is probably because of their lack of ability in placing low-level features with zonal flow like this outside of 48 hrs. I don't think the storms will have a problem staying discrete given the boundary orientation and progged storm motions.

I'll be out and about probably around the warm front along I-70. Hopefully the storms will stay away from KC's traffic and Missouri's terrain.

 

[David Toner]

I agree with Mike Hollingshead, I am thinking currently of targeting SE Kansas. Slightly worried about the weak surface flow and the possibility of low clouds limiting the surface heating. But I'm confident that we should see a few storms that are able to overcome that. Given the impressive amount of instability and shear its a setup to hard to pass on this close to home. As O'Keeffe mentioned above I too am in!

 

[Ken Johnson]

Don't totally write off OK and extreme NW Texas for an isolated fat sup. CIN looks to weaken with extreme instability from Tulsa south down into southwestern OK and NW Texas. There may be some increased convergence in vicinity of the dry line bulge across NW Texas or SW OK. 18z NAM is initiating convection in this area.

 

[Alex Lamers]

Boy, what an intriguing set up. I always enjoyed attempting to forecast these "boom or bust" type events where the big question is whether or not anything will develop; however, if anything does develop it would go up in a big way.

Obviously there is going to be a whole lot of juice available tomorrow, especially across OK. The 18Z NAM portrays widespread 70-75F dewpoints across pretty much the entire state. The 18Z GFS even has a corridor of 75-80F dewpoints from SC into E OK. This could be a bit extreme, despite the rapid green-up we've had, and a lot of recent rainfall. I attempted to use the SREF Plumes from SPC in order to get an idea for a good, reasonable range of values to potentially expect tomorrow. At Norman, in the afternoon, the model mean is 72F with most ensemble members anywhere from 69F to 76F and all ensemble members between 64F and 80F.

It seems reasonable to expect lower 70s dewpoints. With high temperatures forecast to be in the upper 80s to near 90, there should be a pretty large amount of instability.

The biggest problem appears to be a lack of very strong forcing. There will be a pressure trough of some sort stretching from the SW corner of OK northeastward into E KS. It doesn't appear to be a cold front per se as temperatures are relatively uniform on both sides of the front. I guess you could call it a dryline, because there is an obvious moisture gradient, but it doesn't really seem like one. In any event, the density differences shouldn't be too terribly huge and convergence is expected to be weak.

Additionally, 500 mb flow is zonal and any disturbance (if it IS there on the model) is not really discernable. The GFS seems to want to indicate very broad, but very weak rising motion over the Southern Plains in vertical velocity fields.

I know the cap will remain an issue with 700mb temperatures approaching 12C in SW OK and 10C pretty much everywhere in OK. But, the good news is that there appears to be no cap in the forecast soundings. The 21Z OKC forecast sounding from the 18Z NAM run uses about an 86/71 surface condition. It has no cap, but notably there is very little positive buoyancy below 700mb. The CAPE above the 700mb layer is pretty substantial. In any event, this signals a couple of things to me. (1) The setup will get much more volatile (especially tornado-wise) if a few locations can get dewpoints up around 73-75F as opposed to the lower 70s. (2) The tornado threat is somewhat lessened by the limited instability (and thus vertical parcel acceleration) in the lowest few kilometers. However, with massive amounts of CAPE in the -10 to -30C layer, giant hail would be a big concern.

In any event, I suspect that a lack of any substantial cap and the abundant instability will allow for some storms to develop. The weak forcing should keep things more isolated. Only time will tell, but it should be a chaseable event. Unlike Tuesday, I think the cap will be weaker tomorrow. The only problem is the warmer temperatures in the 850-700mb layer may limit tornado potential for a time. As the daytime hours wane, I think the ascent may help cool that layer some (suggested by NAM forecast soundings). Low LCLs and the high dewpoints, along with increasingly curved hodographs after dark may increase tornado potential, but the lack of a strong focusing mechanism could cause everything to fall apart.

Boom or bust at it's best

AJL

 

[CZandbergen]

I agree with most of what Alex has posted above. I have been looking at this one for the last two days. The 18Z runs were disappointing, but looking at the 0Z NAM it looks like things are a bit better. My real concern is what we are going to have around surface winds and what is the forcing mechanism that is going to kick things off. It looks like NC OK and SE KS are going to get veering winds which makes me not like that area. SC OK is still looking to be backed around 0Z tomorrow and all the other factors there look good.

I am not sure I can make that chase area tomorrow, but I think I will load up and head out anyway mid afternoon. FWIW the hodographs in SC OK look very nice. I don't put much faith in the model skewt's as they never really seem to match up with reality. They always seem to under estimate CAP. My plan at this point is to watch surface obs starting tomorrow morning and decide on a target late morning. Just don't feel I can pin point one at this point. I am hoping some falling pressures, sat clear areas, or other interesting data will show up in the real observations that will point me in the right direction. One last thing, humidity is off the charts in Tulsa right now. I don't think moisture is going to be a problem for once...

 

[Mike Hollingshead]

Still liking the ne KS/w MO op tomorrow. A supercell in western IA this evening had a nice hook, tornado warned and produced baseball hail and lived for quite a good while. The setup may not be terribly different tomorrow...just more juice. Nice nw flow setup so veered low levels not a huge deal. Today's storm for example had 20 knot westerly 850mb winds with a nice nw 100 knot upper jet...weak sfc winds. Or course the thing came out of a cluster of garbage and may have been diverted right some by all that. Cooler 700mb temps than down south and nice flow aloft. KC still looks good for a starting point. Just hope it stays out of some crappy terrain in MO before dark.

SZL 0z

 

[David Reimer]

An interesting setup, as usual for May. My thoughts, which are not at all technical, are located at the Texas Storm Chasers blog at http://blog.texasstormchasers.com/.

I feel this image expresses the situation for tomorrow for SC OK.

I'm sure Connor will have a much better discussion later this evening.

- David Reimer
www.texasstormchasers.com

 

[Darrin Rasberry]

I agree with Mike H's assessment above for a warm front play in Northern Kansas with this setup. I'm not able to go since I'm giving my Cal II class a final tomorrow night, but after looking at the recent setup for just a couple of minutes I think somewhere around Olathe to Lawrence may be a good play to catch a cell coming up off that low.

 

[Jared Farrer]

Per 0z run I am now not so sure. Instability is still forcast to be excellent. And now models indicate cap being somewhat less of any issue. But with forecast storm motions and wnw flow aloft I really see the potential staying more with Hail and high winds. The NAM doesnt want to break out precip at all over OK until much later. I dont really foresee this happening though. I am sure something will go up.

But KS may still hold better potential then points further south. Veering 850s though lead me to think hail here as well. Still might be worth going out for. Could see some interesting things. With Instability like that its going to be crazy no matter what. Might be able to get a decent storm up near that low to do something. Shear is alot better right there.

 

[Brian Stertz]

I am going to stay put and monitor things here. You're welcome to stop by H if you need a data stop in KC. Think that whatever happens tomorrow, should develop and blossom within 40 miles of me. All the bigtime severe wx parameters point to KC during the daytime and then NW Oklahoma at night (go figure on that one). Now time for sleep...got to work and then....

 

[Jeff Duda]

I also agree with Mike's analysis of the northern target (which is conveniently much closer to me ). The 00Z runs put something of a warm front running along or just south of the IA/MO border tomorrow afternoon with plenty of directional shear. Just hope instability is good enough up there. Also, hope that the current precip in Nebraska doesn't affect the area for too long and moves out in time for destabilization. I may make a chase down I-35.