5/8/09 FCST: TX/OK

[Michael O'Keeffe]

Friday looks like it may be yet another severe weather event near the Red River and I think this one could be a very productive day. Based on the 12z NAM Cape and moisture will be no problem and the shear looks pretty good with great veering with height creating large forecasted hodographs at Wichita Falls. A nice dryline bulge and warm front are looking to setup basically right on or just a hair south of the Red River and I think anything that can initiate and ride the warm front could produce some monster hail and a few tornadoes.

 

[Darrin Rasberry]

The GFS and NAM are in a *slight* battle over the placement of this, with the GFS putting things further south and the NAM, with seemingly unbelievable 110 degree temps at the surface near Wichita Falls (due to its tighter resolution of the low), deeper into Oklahoma as of 00z. Both agree on the fact that it is just getting too hot down there, but the GFS breaks out precip around Ardmore while the NAM leaves things dry as a biscuit. They do agree on the placement of the bulge, so it will be interesting to see how this one plays out.

 

[Darrin Rasberry]

Day 2 MOD on this setup for central and eastern Oklahoma down to the Red River. I'll be honest here - the setup hasn't really changed from last night, and I guess I'll just have to concede that I don't really have the expertise to understand why there's a significant tornado threat in an area where you can fry an egg on the sidewalk.

 

[Jim Tang]

Day 2 MOD on this setup for central and eastern Oklahoma down to the Red River. I'll be honest here - the setup hasn't really changed from last night, and I guess I'll just have to concede that I don't really have the expertise to understand why there's a significant tornado threat in an area where you can fry an egg on the sidewalk.

I'd suspect the MDT is based on the possibility of giganto hail more than anything. And the fact that NAM breaks out precip in that area (which I strongly disagree with, because the NAM always underforecasts the cap).

IMO the greater tornado threat lies to the east of the MDT risk area.

 

[Scott Hammel]

I'd suspect the MDT is based on the possibility of giganto hail more than anything. And the fact that NAM breaks out precip in that area (which I strongly disagree with, because the NAM always underforecasts the cap).

IMO the greater tornado threat lies to the east of the MDT risk area.

I agree with both you and Darrin. I suspect the MOD was tagged for hail similar to the setup earlier this week. I'm not sure moving east or west of that area necessarily increases chances at tornadoes but it should be an interesting day for sure. GFS appears to push CAPE further east with every run so maybe the Moderate area will eventually move slightly east as we get closer. It's a bit too far for me but I will definitely try to get out to SE CO to see if we can get a storm or two to fire. The wind shear should be pretty high and there should be some decent destabilization as the afternoon progresses. Good luck to all going after the big show in OK though! I can definitely see some windshields taking a beating...

 

[Shane Adams]

We spent a lot of time discussing Friday in the chatroom last night. I gotta admit, I was very surprised to come in here and read the overall skepticism regarding this setup. I don't know what you're seeing on your end, but the current NAM has everything you'd want: great veering with height, insane instability, dewpoint depressions 15-17, and a stout but breakable cap. The h7 temps are deadly further south along the Red River and into Texas, but SC Oklahoma is prime, sitting right on the cusp of the h85 inversion. The subtle difference between tomorrow and the last few setups (May 1, 5) is anvil level winds from 270 degrees, which would eliminate the pesky "inflow seed" issue we've had the past few times on those slow-moving sups that overspread their own surface inflow. Seems like the ventilation should stay a bit north of the inflow region on any sustained sup, which should allow another 5-10 minutes per "upswing" cycle, which could be the difference-maker regarding tornado potential. To my eyes, Pauls Valley, OK is going to be under the gun around 5pm Friday evening. Of course this is subject to change as the next few runs possibly move the target area around a bit, but as of now it's a safe bet SC Oklahoma is the place to be.

But on the other hand, we all know how overrated OK is, so unless you're from here, you'll probably just wanna sit this one out

 

[Brendon Lindsey]

But on the other hand, we all know how overrated OK is, so unless you're from here, you'll probably just wanna sit this one out

Yeah like Shane said, most likely you guys should just sit it out if you have to drive more than three hours to get there... it probably wont produce anything but gigantic hail

I'm going to throw Stratford OK into the mix and say something will blow within 30 miles of there.

 

[Jeff House]

Believe SPC MDT is justified for gorilla hail more than torn, just like it was 5/1 and 5/5. However, just like both days, a lone sup could produce a tornado. Though 5/5 did not produce the sup did put in a good effort.

Should be some pre-dawn rain from north of OKC toward ICT moving northeast during the morning. It will lay an outflow boundary into central or south-central OK. If all goes well the edge of the cap, theta E axis, and intersecting boundaries could be in fairly close proximity Friday afternoon. Little westerly jet max to the north should be close enough to fire off convection.

Now as I type the latest NAM has the best surface convergence farther south and under the cap toward NW TX, which would hurt tornado chances. Even with dewpoints of 65-68, high temps near 100 in NW TX would keep LCLs too high. Now the cap is also shown slightly weaker from CDS to SPS, but overall the 12Z NAM is less friendly to chasers. Much will depend on how well the surface boundaries line up with the edge of the cap. The 12Z NAM is trying to push shallow cool air farther south, which is why it is pushing the boundary farther south and under the cap.

Let your heart not be troubled though. I cannot find much evidence for a cool surface air mass to undercut the cap until Fri night into Sat. No dense cool air is banked up on the Rockies or anything, which would be bad. In fact temps in the central/northern High Plains are running above normal today. Upslope will change that late Fri, but too late to affect my target area before sunset Fri. Bottom line: I will probably target south-central OK. Will keep an eye west of I-35 but believe it will be closer to the Interstate.

Happy forecasting!

 

[W. Grant Dade]

I too love this set up. Shane makes an excellent point on the anvil winds. 12Z NAM looks even better from that point. However, I don’t like the fact the 12°C h7 temps are farther north into Southern OK. Still, with the extreme forecast instability one or two monsters should form. I am not from OK but this set up is too good for me to pass up. I will be heading to Ardmore after work and then evaluate data to determine the best target tomorrow evening. If the current model trends continue I will probably need to move my initial target farther north.

 

[Ken Johnson]

Friday's an interesting looking day and it could turn out to be a couple of good tornadic supercells along or north of boundary. 00z Nam has little to no CIN from SPS eastward along the Red River, with about 5,000 Cape. Wind shear also increases during the evening as hodographs have an excellent low level clockwise turn. The NAM breaks out convection from about I44 eastward. If storms can develop and remain discrete long enough along the boundary where the are NE winds at the sfc, then a couple of big torndaoes could occur, especially if LCL's can lower during the evening...
Friday does look like a good day for people who want to chase down close to the Red River.

 

[Chris C Sanner]

Yuck! Are those NEly surface winds? Say bye-bye to any chances of tornadoes if that verifies...at least in the currently outlined area of max severe potential in the latest SWODY 2. I may be wrong, but I seriously doubt there has ever been an organized tornadic event with winds out of the NE at the surface. The 850 winds are absolute trash as well, 15-20 kts at the most.

Otherwise, the extreme instability will be there, so maybe a cell could manipulate it's environment and create it's own wind field. Given the 850 winds though, not sure if that's going to be able to be enough. But regardless, if those NE surface winds verify as per the NAM, we're going to be seeing another setup down the drain.

EDIT: Looks like the NEly surface winds are because of an outflow and/or an elongated area of low pressure in Texas....at least it appears so. The environment south of the red river looks a bit more favorable with SEly surface winds...but the cap is also stronger. In summation: The NAM pretty much sucks tonight for tomorrow.

EDIT EDIT: And the GFS is in and the main body of Oklahoma is definitely out of the picture and the best parameters are into Texas...where a very tough cap is in place. We just can't win this year.

 

[Darrin Rasberry]

But on the other hand, we all know how overrated OK is, so unless you're from here, you'll probably just wanna sit this one out

Like we like to say, OK is overrated ... until the next time we drive out all the way to chase it

Craig is on his way to SC OK from ICT tomorrow; I will be stuck here grading a stack of finals, though. If I were there I'd target just east of Wichita Falls to catch a boundary/front rider along the river, where the winds will be ESE. Anything over that boundary might produce some awesome hail, but the tornado play is going to be along the Red River tomorrow right on that boundary that will be aided by the (now PDS SVR!) complex of storms that Alex pointed out above.

 

[Brendon Lindsey]

Well I believe there will be a supercell fire within a triangle Ardmore, Ada, Atoka. Ill be there. Well I'm going to hope for the best. Hope I dont have to go into to many tree'd areas. Thought this was interesting around 22 hour.
http://www.emc.ncep.noaa.gov/mmb/mpyle/cent4km/conus/00/

Brendon L.

 

[cstrunk]

Well, kind of a surprise target is taking shape for this afternoon. Central Iowa looks to be an area of interest for an isolated tornado. The SPC has upgrade the area to a slight risk (from nothing previously) including a small area with a 5% tornado probability area in the center of the state.

There was some clearing earlier today that has boosted temperatures to around 70F and dewpoints in the upper 50's. There's a good cumulus field building up all around me here in Ames, with some showers and weak storms developing to my northwest.

I'm going to stay put here in Ames and if something interesting develops, I will probably head out for a local chase.

Thoughts?

 

[Brian Stertz]

Seemed like yesterday was chase "one storm in" from the cap and it should do something. So reading the NAM, it would say that the Sherman-Bonham TX area would be the area under the gun today with this in mind. Although LL winds on weak side, as Shane mentions you do have good veering and instability. Best of luck to those going out today down towards the forecasted boundary on the Red River.