5/19/2010 FCST: TX, OK, KS

[dmckemy]

Latest GFS (12z) run indicates a decent severe weather event for this Wednesday...The GFS develops a surface low off of the Rockies (in response to the upper level trough/cut-off low moving into the area), and parts of Northern TX/Western OK/Western KS have good CAPE (1000-3000), decent wind shear (40-50kts of 0-6km shear) and large clockwise hodographs. While it's too early to get into the specifics on where the greatest severe weather threat willl be, it's definitly something to keep an eye on over the next few days...

 

[Chris Hayes]

I was thinking about starting a thread for this day as well. It does look very interesting. The GFS has been hinting at possible chase opps starting on wednesday for a few days now. As the week goes along it appears chase chances will continue through Friday albeit moving south and east, but Wednesday is looking quite interesting. It doesnt appear that moisture advection will be a problem with DPs well into the 60s ahead of a fairly sharp dryline.

 

[Matthew Piechota]

Its been interesting to see how the models have been handling next week where a few runs ago the GFS was showing a ridge over the central plains where the euro was showing a ULL coming out into the plains in this timeframe and the last two runs of the GFS has been coming more in line with it showing oppurtunites for some good chasing setups next week.

nice H5 flow as the trof moves in with the low coming off the rockies with moisture and instability not being a problem with great flow into the area. will be interesting to watch and see how the models handle this over the next few days.

 

[Greg McLaughlin]

Wednesday has real potential. Could this also be an OFB day? Its interesting how a few days ago the GFS was very aggressive developing a large ridge over the central US this coming week, and now it is backing off of that and delaying the ridge for another week or so. I remember last year when we were under the ridge in May the GFS was very aggressive in breaking down the ridge and developing a large trough over the western US. The GFS kept delaying the trough development for several weeks before it finally materialized in June. I am hoping it does the same with the ridge this year.

 

[Greg Blumberg]

Now that I am free from exams, I can do some forecasting for next week.

I agree that Wednesday has potential, especially with the upper level jet streak being thrown out by the models. With it's left exit area placement over the warm front, and the 0-6km shear vectors oriented generally parallel to the warm front boundary, something could fire and latch onto the boundary. From what I've seen in the models today that seems to be the setup so far, and from what I'm told the models seem to be very consistent in producing an event Wed near the Wichita Falls area (and maybe a bit further south and maybe westward.) I will be watching this setup very carefully over the next few model runs.

 

[Chris Wilburn]

There will be plenty of moisture and instability for sure. It's nice to see that won't be an issue. Looks like a nice dryline and warm front will setup somewhere in the eastern TX panhandle/NW TX area as a general area right now. Directional shear looks really good and the speed shear is good enough for tornadoes without the insane storm speeds. The shear forecasted is actually the way I prefer it. 40kts at 500mb can produce some really nice tornadic supercells. It will be nice to actually get out and film via tripod for once. Still a few days away, but looks good so far.

 

[Matt Grantham]

Have been watching this potential threat for several days now as I will finally have a few days to chase. This one looks more than worth the drive from Corpus Christi. Moisture, CAPE, and shear look great with a nice jet streak nosing in during the afternoon to trigger the storms. Rather large clockwise curved hodographs should promote a sizeable tornado threat with supportive LCLs. Storm motions will be relatively slow and will make for almost a perfect setup for the type of chasing that many of us enjoy. Could be the ideal day for Vortex 2. Hopefully the models will remain status quo or trend more impressive up until the event.

 

[Chris Wilburn]

This day has shown up the last couple of days now on the GFS. The NAM will pick up on it at 12z in the morning. The past couple of days have been pretty consistent in setting up a warm front along the red river and points north into OK. Also, the models have been showing a dryline setting up in the eastern TX panhandle/NW TX area. Dewpoints near 70 and SBCAPE well over 3,000 J/kg will create a very unstable atmosphere. Hodographs for the SW OK area show very nice directional shear. Speed shear is adequate as well, but not too extreme which is nice at times. 25kts southerly 850mb flow and southwesterly 500mb flow at 40kts appear to be in place for this day. I pulled up a sounding for Hobart and it shows only 25kts storm speed which is really nice to see! Cap doesn't appear to be a major issue with this day as well. Forecast sounding for Hobart only shows about -35 CINH left at 00z. SRH and EHI values look great as well. Supercell potential is at 98.7% and lcl height are very low at less than 700 meters. Storm direction is 244 degrees which is more of a east/northeast storm motion rather than northeast. This may help a storm latch onto the warm front and go nuts. This day has promise for sure. Hopefully the NAM agrees in the morning.

 

[Chris Hayes]

Both the GFS and NAM continue to show a possible severe weather event for Wednesday, the difference is location. If the the GFS verifies central and western Oklahoma will be the place to be. If it's the NAM it'll be western north Texas. NAM shows a negatively tilted trough combined with MLCAPE up to 2500, 1KM SRH of 100-200, 1KM EHI up to 3.6, and 3km EHI up to about 7. Cap is there but breakable. Forward storm speeds will be very manageable. Target would be from east of Childress to Quannah.

GFS is a bit more progressive and doesnt show a negative tilt with the trough. Still, a very unstable airmass would be in place across western and central Oklahoma and north Texas. Cap is a bit more stout on the GFS but it still shows what could be storms developing. The cap appears to get stronger over the night though, so how long storms survive in that environmnet would be in question. Target would be El Reno to Clinton, OK.

 

[Ben_Jacobi]

You guys have pretty much covered it. Something that stood out to me on the 00z NAM was a nice DL bulge in TX. This will add extra convergence and is right along the instability axis. With the cap erroding and plenty of moisture, I bet we see a nice beefy supercell just ahead of the bulge. I will be asking off work for Wednesday. Its still a little early, but if I had to pick a target it would be Paducah, TX.

 

[James Aydelott]

Northward expansion of the instability will be a real issue on Wednesday.

Sure looks like a major league severe weather outbreak for SW OK and NW TX. A lot will depend on Tuesday evening convection too.

Storm motions will be half the speed of last Monday.

 

[TimothyCarroll]

It may be a little bit early for me to really try to nail down this one, however, I have to agree with Ben, the NAM is setting up a really nice bulge in the dryline along and just south of CDS, with very light precip breaking out, at around 21Z, Sfc Td's are in the upper 60's and Temps of low to mid 80's, I believe both of which may be a little higher than the NAM is forecasting for as well. Good strong 25-30 kt Sly low level inflow, and a warm front setting up along the red river, with MLCAPE Values as high as 3500 J/Kg, and CINH Values very reasonable for this type of setup, very easily broken CAP, Right along and Just SE of the forecasted bulge in the dryline, I would not be to terribly shocked to see a nice supercell fire right along the SE sector of the buldge, get rooted and just go hog wild, Storm Motions seem to have slowed down a bit too, giving ample time to mature. Very Chaseable if I may say, But again, its still a little early, If I had to make a wild card guess, I'd target The area between Childress, Quanah, Crowell, and Peducah, TX . . . .

 

[Greg Blumberg]

This is a very tricky forecast because the trough is onshore, well within the data network, and yet the models are still exhibiting some pretty significant differences. Both 12Z models have not initialized the 500 mb jet streak well per the 12Z upper air data. It seems they have been having some trouble placing the 60 knot jet core.

As for the model differences in the setup:

GFS - has the dryline placed over the Lawton/Wichita Falls area. It's being more aggressive with the warm front, pushing it parallel to the KS-OK border. It looks like the model has an MCS forming later on in the night. Additionally, there is a nice widespread area of 3000+ CAPE across the warm sector, with some pockets of 3500 in some of the less-desirable chase territory. I can see something discrete and maybe isolated going up, especially with the cap being eroded like it is. The nice thing is shear between 40-50 knots perpendicular to the dryline which is more than sufficient to get supercells going in this CAPE-filled environment.

NAM - dryline is shifted to TX/OK border. Warm front is not as far north compared to the GFS. CAPE is not as extreme as the GFS, but rather around the 2000~3000 range. The NAM has the cap completely eroded across the Oklahoma area by 0Z. 0-6km shear is like the GFS.

LCLs look fine for both. For both models, the low-level shear is placed much further east. Neither model has a very prominent low level jet that would scream tornado outbreak to me. For the NAM, this has been the first time that it's advertised such a weak low level jet. The GFS has been pretty consistent on a <=30 knot low level jet. I'm hoping this NAM run is just an anomaly. The CAPE values may suffice for this, but I'm not a very sharp forecaster when it comes to forecasting high CAPE/low shear environments. I do not doubt that there will be tornadoes tomorrow. Perhaps the models will converge on a solution come this evening's 0Z runs.

 

[Russ Conlon]

18Z NAM seems to be coming to agreement with the GFS in regards to dryline placement. Now showing a far more aggressive dryline bulge into west central OK between Clinton and Highway 81 by 00Z. Won't discuss the other variables as everyone has already pretty much run through them on this thread. Right now I am targeting Anadarko, OK pending any further changes but this is looking like another very nasty tornadic setup for central Oklahoma again.

 

[Chris Hayes]

I'm camped out just east of OKC right now. My main concern with this setup is any residual cloud cover left from tonight's convection and MCS activity. Aside from that it's nice to see some model agreement finally occuring. Been nice had it agreed to a slightly further west solution, but it'll work. NAM predicted 0-1km helicity and EHI is not overly impressive just ahead of the dryline but 0-3km for both, and 2000+ CAPE appears very conductive for supercell thunderstorms. Hopefully the storms that could move through tonight will throw down some boundaries for a storm or storms to ride along tomorrow. Will Be targeting a line from Clinton to Lawton if things stay the same.