3/8/10 FCST: OK / KS / TX

[Jeff Snyder]

There may be two possible plays for Monday, at least according to the 12z GFS And 00z EMCWF from last evening... The first would be the more typical warm-sector play primarily along and E of I35 in the southern plains, as a strong mid-level low moves into OK (12z GFS) or KS (00z ECMWF). As is common for this early in the season, it is likely that low-level moisture will be quite marginal. The second area, which is the area that has my attention at this time, is a possible "cold-core" play... Looking at the 12z GFS, this setup screams "cold-core low-topped supercell" to me. For example, using the 12z GFS output, 500mb temps may well run colder than -25C as the mid-level cold pocket moves into Oklahoma and maybe far southern Kansas. Underneath and to the northeast of the the mid-level cold pocket, I'm seeing very backed low-level flow (E or ESE) with dewpoints in the mid-upper 40s across south-central Kansas (early afternoon) and southeastern KS and adjacent parts of northcentral/northeastern OK (mid-late afternoon) to the northeast of a <996 mb low. The specifics of whether we'll see enough insolation to create steep low-level lapse rates (which will then affect the 0-3km CAPE) can't really be known this far out (hey, it's the 126-132 hr forecast from the GFS!), but pattern recognition (e.g. March, strong closed mid-level low with associated cold pocket plowing into the southern Plains, strong surface low with very backed low-level flow to its northeast, very marginal dewpoints for "typical" warm-sector convection, etc.) is leading me to watch carefully the OK/KS border area for a potential "500 mb cold-core, closed low" low-topped supercell setup.

I should note that I don't have access to the higher-resolution ECMWF forecasts, other than the very limited selection of low-res products on CoD's site. The latest ECMWF that I can see (again, off CoD) has the mid-level low and surface low farther north (primarily in KS), which would push the threat for low-topped supercells in the "500mb closed, cold-core low" conceptual model to the north accordingly. It's hard to get excited about Tds in the 40s, but that's all it takes in these types of setups (I vividly recall watching a tornado in Dewey Co in March 2006 with Tds in the low 40s and heavy snow falling ~30 miles to the NW).

EDIT: Thanks to Buddy Bradley for pointing out that I somehow forgot about the whole "new year" thing. As such, the year has been changed from 09 to 10. Doh!

 

[Skip Talbot]

I've been watching this setup for the past few runs, and the GFS has been all over the place, flip flopping radically from run to run. It is showing a nice cold core setup every other run, however. This morning's 12z run is again great over southern KS and northern OK as Jeff pointed out.

Low 50's Td's wrapping around the surface low:
http://www.twisterdata.com/data/mod...S_3_2010030312_F126_DPTF_2_M_ABOVE_GROUND.png

Vertically stacked with a closed low at 500 mb:
http://www.twisterdata.com/data/mod...3/03/12/GFS_3_2010030312_F126_TMPC_500_MB.png

The low 50's dewpoints wrapped around and under -25 temps at 500 mb spell out classic cold core setup if this verifies. There is even 750 j/kg of SBCAPE being plotted, which is great for a cold setup. If the GFS verifies, then we could definitely have a shot at some tornadoes in the plains, but again, the GFS has been all over the map. The 0z run had the stacked low way up on the KS/CO border, and the 12z run yesterday was much faster, ejecting it over the midwest. I won't be seriously eyeing this setup or picking out a target until the NAM is in range and in agreement, but this is definitely something to watch.

 

[Jim Bishop]

Yeah, the operational models have had a hard time this week timing this wave out of the eastern Pacific. From what I've observed over the last three days the European (and even the Canadian) model has been much slower to eject the wave into the southern Plains Monday. The GFS has sorta caught onto that idea over the last couple runs.

Perhaps the slower trend will continue? I think it could considering the wave will be a closed low near California for a couple days, and normally these types of systems eject slower than models initially suggest.

 

[David Goines]

The 12Z GFS was really surprising with the closed low over the Red River 108hrs out.
Really nice CAPE for this time of year also.

http://www.twisterdata.com/data/mod...010030412_F108_CAPE_180_0_MB_ABOVE_GROUND.png

If the GFS continues moving the low south every run, it'll be down in Brownsville by the 8th.

 

[W. Grant Dade]

I like how the GFS is slowing things down a bit. At 84 hours the NAM and GFS have the trough pretty much in the same position. As David mentioned the CAPE is fairly high, peaking over 1300 J/kg on the GFS. Also the GFS usually under estimates the amount of return moisture in East Texas this far out. Right now we are seeing dewpoints progged to be in the lower to middle 50s. I think the 60 degree pewpoint line will make it at least to I-20, maybe I-30. This would increase our CAPE. 0-1km SRH is off the chart in the early afternoon. Bulk shear is between 50 and 70 knots. 0-3km CAPE approaching 300 J/kg. Overall a pretty good set up but I would like to see the dryline move through about 4 hours later so I can chase the event. If not I'll be stuck at the station.

 

[Jim Bishop]

I'm not too optimistic about the setup across the warm sector in Texas - it looks messy. Closed upper lows usually don't provide great shear/setups for supercells in the warm sector, and this setup isn't much different. But things could still change.

The cold core setup may hold more promise, but it's too early to speculate on that right now.

 

[Tony Laubach]

The 12z NAM makes western Oklahoma look pretty interesting with the values its trying to spit out with the closed circulation. As Jim mentioned, may get a bit cloudy, but the areas further north may see some interesting setups based on this run. CAPE values may be a bit high, but its hinting at 1000-1250 in a narrow ribbon from roughly Wichita Falls to Altus with good helicity values. Not a bankable forecast, but more promising than it looked when the GFS has the system clear down in south TX (more promising for us Colorado folks that may opt to make the drive).

 

[Matthew Piechota]

If the warm sector can clear some things could get a bit interesting from SPS on into western OK looking at the 12z NAM. going to be good shear with 50-55 Td's nosing into the area with CAPE values as Tony said, greater than 1000 j/kg with backed sfc winds.

the 12z GFS has 750-1000 j/kg from north TX on up into western OK, the cold-core setup will also have possibilities but still a few days out.

Its nice having a setup to watch unfold, were getting closer.

 

[jamesmseitz]

I too have been watching this for awhile and to me things are not coming together. GFS has moisture breaking out early. Clouds will probably to thick for any good heating and with the moisture staying closer to the coast a regional servere weather at best. Have to admit that it is showing the change is coming.... the season is almost here ....... Gotta love this stuff

 

[Darren Wilson]

This has some potential, but I'm afraid some of it will be trapped under thick cloud cover. I really like the upper level winds with respect to the location of the dryline per the 12Z GFS. However, the fast H5 winds will likely result in very quick storm motion. IMO, Southwestern OK and Western North Texas looks like the best bet right now.

 

[Skip Talbot]

The GFS and now the NAM have been trending negatively since I last posted. I was hoping to get more of a classic cold core setup out of this system, but that doesn't look like its going to happen now. With the system continuously slowing down, the cold air aloft doesn't overtake the surface moisture wrapping around the low until after dark now. With that we lose our daytime heating to get the low level lapse rates we need to make this cold core setup work. As others have mentioned cloud cover and precipitation in the area is going to further inhibit destabilization it looks like. In order to make something out of this you'd have to look at a more convenctional warm sector target. Instability is going to be low thanks to the lack of heating and marginal dewpoints. Although the 1000 J/Kg plotted at 0z might be enough for some storms to get up, the window of time that instability hangs around is only about 3 hours or so. It looks like the cold air aloft comes in in time to destabilize the area, but we quickly lose it after dark. Storm motions are also going to be cold core like, with a mostly north component. This isn't bad if any storms can put out a show right after initiation, but they will quickly cross into cooler and more stable air afterwards. I think there is still a chance for some isolated severe weather in western OK and into TX, but at this point I've ruled out any chance of making a marathon haul out to the plains.

 

[Jeff Snyder]

I agree completely with Skip, and I was going to post almost the exact same set of thoughts... With a delay of the low cutting off and moving into the Plains, the forecasts from the NAM and GFS this morning no longer really look like a more classic "cold core" setup. The 12z NAM has the sfc low in very extreme western Oklahoma panhandle (and adjacent portions of northeastern NM and southeastern CO) at 00z Tuesday (i.e. Monday evening), with the "bent-back" region in southwestern Kansas (actually N of the 500mb cold pocket). The 12z GFS is a bit farther east with the system, still looking to support a possible "cold-core" setup in the far SW KS / NW OK area (where sfc moisture stream arcs back towards the sfc low). Both models are forecasting >90% RH at 850mb (i.e. low clouds), with light to moderate QPF throughout the day, which will keep temps relatively cool. There are some indications that clouds may break up in western OK and W N TX by mid-late afternoon, but I'm not sure if that'll be too little, too late.

I've been suckered many times by meager (and evidently insufficient) low-level moisture in the "warm sector" (the more classic area of chasing -- east of the dryline / Pac front) on these early-season 500 mb cut-off low situations, and I don't think I've ever had any real success chasing 52-55F tds. As such, my focus continues to be on whatever potential opportunity we have for "cold core" action. Again, with these "types" of setups, 45-55F Tds are just fine. Unfortunately, as Skip noted, the forecasts have turned less favorable for such a chase situation. At least we're still 68-70 hours out...

 

[Connor McCrorey]

Based off of tonight's NAM, I'm thinking central Texas might be a good warm sector chase if everything comes together. I have a feeling that it won't, and obviously a lot will change, but I posted a very brief update about my thinking for Monday at http://www.texasstormchasers.com

EDIT: I'm a total noob at CC forecasting. I kinda get it, but a lot of times I won't see even when there's a lot of potential, so any constructive criticism would be very appreciated.

EDIT #2: And of course there goes the GFS, bringing back the cold core idea in Oklahoma. Woohoo.

 

[jamesmseitz]

I just did a good look at the lastest SREF as well as NAM. I do not see it....... There is a Week Dry line in Texas but the temps are going to stuggle to break 70. Cloud Cover will be thick in OK with the bulk of the Instibility will happen after Dark..... with temps heading down in the 40's. There are a few soundings for the tale end storms in Central TX where shear is good if they can get up there..... The Lift is poor except down by the Mexico line. I really am not believing in this one at all any more. To many things against it. There will be storms and that is a great sign of things to come but am I missing anything..... Teach I want to learn because my years say 5 % at best

 

[Chris Wilburn]

After looking at the 00z run of the NAM this evening I was thinking central TX may be a decent play. Dews. were near 60, but the best southerly 850mb winds are in northern TX with veered 850mb winds where the best moisture is in central TX. Also, CAPE is almost non existant unless you head to southern TX and I imagine that combined with moisture arriving late and moisture depth lacking we will most likely be looking at elevated storms. I wasn't planning on chasing anyway, but if the 850mb winds can be more southerly where the best moisture is and CAPE increases a bit there could be a threat for a few tornadoes.

The GFS basically says the same things in regards to moisture and the 850mb winds. The GFS has the best moisture near or just south of the Dallas area, but the 850mb winds are veered to the SW. The best southerly 850mb winds are north into OK and away from the best moisture and instability.

It's nice to have thunderstorms in the forecast again and I will be looking forward to hearing some rumbles of thunder in my area of NE OK. It looks like this system will kill moisture for several days and I would look for the last 12 days or so of March before it begins to rebound somewhat. It will only be a matter of time that we see a good system come through where moisture and intability aren't the main uncertainty. Also, a week from now we will have an extra hour of daylight to work with. I am glad we are given this in mid March now instead of early April like it used to be. Hopefully we can benefit from this sometime in the last 10 days of March or so.