10/22/10 FCST: OK/TX/KS

[Chris Wilburn]

Friday has the potential to be a fairly decent chase day with the potential for tornadoes. The NAM looks solid for SW OK/NW TX while the GFS has things looking somewhat interesting as far north as N OK/ S KS. Limited instability around 1,500 J/kg and no CAP/early convection are the two main concerns. I am not really that concerned with the CAPE as 1,500 will be just fine with the amount of shear that will be available. Looks like a classic March chase to me. Based on the NAM low to mid 60 dews possible in the SW OK area with maybe close to 2,000 CAPE. The speed and directional shear in this area are very impressive as well. CAP appears that it will not be an issue and if things can hold off and stay isolated we may be in business. I guess limited daylight may also be an issue, but it's hard to get picky with Fall and early Spring setups. I am not going into many other details, but I did want to get this thread started so others can chime in.

 

[Jim Bishop]

Yes, the shear and moisture look great. The big issue will be morning to midday convection as warm air advection and strong vorticity advection cause tons of t-storms and rain, especially in the morning across western Oklahoma and Texas. If a good clear slot can develop then some pretty nice supercells with a tornado threat looks likely across western Oklahoma in the late afternoon. Definitely a setup to keep a close eye on.

 

[Jacob Ferden]

The moisture does look very good for this deep into October. My biggest concern, other than morning convection, is that the GFS and NAM paint different pictures regarding the shear profiles.

The NAM looks quite good across NW TX / SW OK, with good shear profiles and CAPE aoa 1000 j/kg., and it also should be noted that it currently has a 0-3 km EHI max over that area. This suggests a good possibility for supercells. The tornado threat in this scenario remains uncertain, IMO.

The GFS, on the other hand, shows veering 850 mb winds, and, in my experience, more often than not that doesn't produce a good result. It is more bullish on the CAPE, but the overall picture leads me to wonder if the result will just be a squall line.

Will be interesting to see if the models come into better agreement on this, but it's certainly worth keeping an eye on as we get closer to Friday.

 

[Tom Dulong]

The NAM looks quite good across NW TX / SW OK, with good shear profiles and CAPE aoa 1000 j/kg., and it also should be noted that it currently has a 0-3 km EHI max over that area. This suggests a good possibility for supercells. The tornado threat in this scenario remains uncertain, IMO.

If the NAM does verify...we may have a scenario that pans out like the severe weather event of October 19th, 2005 [Ref link below].

http://w1.spc.woc.noaa.gov/exper/sref/frames.php?run=2010102009

A handfull of tornadoes were produced in SW KS/NW OK near the surface triple point.

 

[Stephen Jones]

Friday is gonna be a very interesting day. As noted, I think the main problem will be the precip in the mid morning to afternoon hours. The 12Z NAM and other models run show a clearing in W, NW, SW OK and SW KS near the triple point. Storms should fire with 1250 JKG of CAPE in the area and should form a line of supercells somewhere in that area.. Couple of tornadoes i see possible, esp W to NW OK and S KS. The threat though will heavily depend on daytime surface heating. This reminds me of the Hammond, OK tornado in March this year.

 

[Marcus Diaz]

I'm loving this setup, especially for October. According to the NAM, all precip should be pretty much done with around noon. Hopefully the cloud cover won't be as bad. The shear looks amazing south of I-40 in W OK. The Skew-Ts in that area are hard to ignore, with very nicely curved hodos in the low levels. I wish the instibility looked better but ~1500 is still good considering the morning convection. And it should be sufficient with the shear that's available. The NAM is breaking out huge supercell(s) in W OK at 0z that track NE. It holds the storm together through 03z into central OK, where the enviroment still looks great. Storm motions look decent with a NE movement of about 10-20kts. I'm not going to rely totally on the NAM composite reflectivity, but it does give a good idea on storm mode for the day. You can bet I'll be out there for this event, Oklahoma or bust!

 

[Skip Talbot]

Given that everything else looks like it should be in place, the forecasted cape values, although modest, are sufficient for supercells/tornadoes. However, the models have been consistently showing a very narrow instability axis. That's my primary concern with this setup. The areas of 1000+ cape are about one county wide. Will the storms be able to mature, and produce before moving off the instability axis? This setup has the potential to go either way. The clouds/precip could clear out a few hours before the event, and bam, we've got tornadic supercells just like March 8. Or it could stay socked in all day and we wind up with nothing. I think its great a play for those within strike range since they can monitor the morning trends before committing, but it will be a gamble for anyone making a marathon run.

 

[Jonathan Whitehead]

I pretty much agree with what everyone else has to say thus far...dont really have much else to add except I am amazed in the similarity in the NAM/GFS/SREF in 500mb winds across SWRN OK/NWRN TX by 18z. All three have a 50kt wind barb over that area. The GFS seems to be a little more bullish on strength/direction of 850 winds over this area than the NAM. The SREF suppercell probs are quite high across this area as well, but its sig tornado probs suck. The hundred million dollar question of course is how the morning MCS will evolve throughout the midday hours. Think were going to have to wait for another model run or two before that picture clears up a bit. IF we can get some clouds breaks across SWRN OK/NWRN TX, I think perhaps a MDT risk will be in order as the shear profiles are quite supportive of a tornadic event.

Ive written more detailed in depth discussion in my blog (see sig)

 

[Chris Wilburn]

Given that everything else looks like it should be in place, the forecasted cape values, although modest, are sufficient for supercells/tornadoes. However, the models have been consistently showing a very narrow instability axis. That's my primary concern with this setup. The areas of 1000+ cape are about one county wide. Will the storms be able to mature, and produce before moving off the instability axis? This setup has the potential to go either way. The clouds/precip could clear out a few hours before the event, and bam, we've got tornadic supercells just like March 8. Or it could stay socked in all day and we wind up with nothing. I think its great a play for those within strike range since they can monitor the morning trends before committing, but it will be a gamble for anyone making a marathon run.

Yeah that instability axis sure isn't very wide from west to east. It's definitely a gamble for sure. Shear continues to look very nice so I am not worried too much about CAPE if we only get just over 1,000 J/kg. I would hate to see a scenario where a nice supercell finally matures and only has about a county to go before it falls off the instability. I think it's worth a gamble, esp. if you are close and can monitor things as they progress throughout the day.

 

[Jesse Risley]

The 00z model runs from last night continue to depict a conditional and rather marginal axis of instability on Friday. However, I did notice the GFS wants to be aggressive on the punch of drier air, as evident on the 00z run's 700 mb RH < 30% working into NC TX and W OK.

It's a rather impressive system with H5 temps approaching approaching -17C per the 18km suite, centered over far SW KS working into a region that could yield SBCAPE values AOA 750 J/KG across C/SC KS into OK. I think the real key tomorrow will be to continually monitor how the instability situation evolves given that the latest runs continue to show ongoing precipitation across much of the region during the morning hours.

 

[Skip Talbot]

The NAM and GFS are both in good agreement that two mid level speed maxes will push through portions of the southern Texas panhandle into Oklahoma on Friday. The first will cross into Oklahoma around noon and the second in the early evening. The dryline looks like its going to be established early, the instability peaking early-mid afternoon, and with little to no capping. You might want to be at your target area by early afternoon in case that first speed max fires storms off. The GFS is plotting blips of precip near the dryline starting at noon. The NAM holds off on firing stuff until 21z - 0z when the second speed max comes in, and probably also because it doesn't push the morning junkvection out until later. Either way, your ingredients are in place by early afternoon so don't be late. The best speed shear will be associated with the speed maxes in these shortwaves. It also looks like the best instability is going to pool in the southern portions of the panhandle. I'd target Paducah to Wichita Falls, TX depending on where the dryline sets up as the NAM has it a little farther west than the GFS. Instability looks like its going to be iffy with the NAM showing 1500-1000 and the GFS 750-500 (yeesh). I'd guess SPC might go with a categorical slight risk on the day 1 outlook with conditional threats for severe weather given the questionable amounts of instability.

 

[Andrew Pritchard]

Obviously not chasing this one, but I'm curious about a SW Kansas target and would likely setup down there rather than the more obvious Oklahoma target that has been discussed thus far in this thread.

I like the odds at the potential for a low topped supercell or two to produce a few tornadoes shortly after the lunch hour from around Garden City south to Liberal, KS. Time frame for this would likely end up being from around 17-20Z. Pretty steep low level lapse rates in this area, should it be convection free during the late morning hours. Given decent insolation, the area under the upper level 500 mb cold core just ahead of the developing surface cyclone could see a brief window of opportunity for a couple little tornado producers that Mike Umscheid will have all to himself as everyone flocks to western Oklahoma.

I've only had time for a brief glance and will try to dive in a bit more this evening and into tomorrow morning when things become a little more evident. That said, even after just a brief glance SW Kansas certainly has my attention as the surprise action area of the day. Say I were chasing the event tomorrow, I'd be shooting for Garden City, Kansas at 1-2 PM.

 

[James Gustina]

I'm going with the consensus on this one. The 12Z NAM had the dryline sitting right on/slightly west of Lubbock in the early afternoon with that thin instability axis of 1250-1500 j/kg of CAPE right southeast of Lubbock. I'm wondering if the GFS and NAM are gonna come into more agreement here with the 18Z run, because right now it looks like sitting between Lubbock and Midland in say, Lamesa wouldn't be too bad of an idea, since it's right smack dab on that instability axis with some relatively good speed shear right along the dryline.

There's my 2 cents, we'll just have to wait and see in the later runs I guess.

 

[Jonathan Whitehead]

I agree with Skip on this one. The SREF has been consistent in showing a peak heating speed max coming into NWRN TX. Instability is still lacking but again shear is more then adequate. H85 winds wont be terrible but not got great. GFS is actually a little more bullish with the directional turning.

IMO with that vort max coming in at peak heating, im fairly certain there will be storms (granted if we can get enough breaks in clouds from morning convection, which im fairly optimistic will occur). What happens after that remains to be seen. While Im not going to be able to chase this one due to a number of factors, I still think an LTS-SPS-CDS triangle is going to be a good play for tomorrow.

For those interested in a more detailed discussion complete with maps and images, please see my write up in my blog.

 

[Greg Blumberg]

Hand analysis reveals a warm front running a bit south of but parallel to the Red River. South of the warm front, an airmass contains dewpoints greater than 60, with most being in the mid 60 range. A dryline extends from eastern Colorado into Southwest Texas, with the warm front intersecting it southwest of AMA. In the wake of the convection, a meso-high has formed along the western border of Oklahoma. Cloud cover covers a good majority of the S. Plains, with breaks in the clouds east of the dryline.

As the day goes on, the 850-500-300 jets should couple, forming a deep surface low over SW Kansas. The warm front should lift northward in response to surface low development. Additionally, a small vorticity max can be seen in the water vapor over eastern NW which could initiate dryline storms near AMA within the next few hours. In addition to the current jets, confluence upstream of the main trough axis should continue to maintain jet development within the base of the trough.

Capping remains to be the real issue in this setup. 12z soundings display an atmosphere generally uncapped, however 700 mb winds could advect warmer temperatures from southwest TX to help produce a cap over the air mass south of the warm front.