05/05/09 FCST: OK/TX

[Jacob Ferden]

While its still several days out, it looks like Tuesday could potentially be a good day per the 12z GFS. Warm front advances north to Southern Oklahoma and a triple point set up in western North Texas. Good moisture return with Tds in the neighborhood of 65 F as far north as far southern Oklahoma, with a pool of 70 F in North Texas. (won't believe the 70 F til the NAM picks up on it). Also an area with CAPE in excess of 3,000 in North Texas. Will have to wait and see how the shear begins to look over the next couple of days, but its certainly something worth watching.

 

[Ilya Neyman]

Progs continue to point to a very synoptically-possible severe weather/tornadic episode for the Red River Valley region Tuesday afternoon-evening. Of course, mesoscale details will be key with any possible evolution of such an occurrence but the few runs I just pulled up, namely NAM and GFS show good consistency/agreement. A warm front and/or outflow boundary combined with superb (forecasted) flow throughout the entire depth of the troposphere along with an upper-level disturbance and favorable jet structure all point to a substantial risk of significan severe, provided ingredients come together. Yet again, the most likely region may be centered on the Red River zone which seems like the popular pattern of late. The zone may be further north or south depending on actuality.

I expect this thread to start becoming quite popular in the coming hours.

 

[Derek Weston]

I expect this thread to start becoming quite popular in the coming hours.

Agreed.... I think this setup has some good potential -- just commented via PM to another chaser that it seems odd nobody is talking much.

But we're going to have good deep layer shear finally and some really good 0-1km helicity in the vicinity of the stalled out boundry in S OK... should things come together correctly, ingredients may be in place for some nice sustained tornadic supercells. (and given the parameters, perhaps tornadoes on the strong side)

Warm temps at the 700 level have me wondering about CAP issues...(though the NAM pops convection by 0Z)

Another concern is that the best low level shear appears to be north and east of the best CAPE... (which sets up against the DL) so perhaps timing issues with initialization off the DL and realization of better sheared environment... (depends on timing of DL initiation, I guess)

 

[Mikey Gribble]

I posted on it this morning on my blog. If you're interested here is the link and it's the second post down....
http://loadedgunchasing.com/blog1/

I have barely looked at this setup, but there is a small area with strong instability, excellent directional shear and high dewpoints. The only thing that bothers me is that I don't see a focused area for convective initiation immediately ahead of this instability axis. There is a kink in the isobars that wraps the moisture (very high theta e air) back around like it would look on a surface low just on the west side of the instability axis. Is this going to serve as a focus for convection? I don't know. I would think therer would be a fair amount of moisture convergence given the directional and speed changes in the surface winds.

I'm going to wait until tomorrow to really look at this, but I agree there is an area that could support some solid tornadic supercells if storms can fire early enough to take advantage of it. It's a long haul for me, but I'm game if I feel confident a storm is going to fire in the right place.

 

[Jason Young]

It seems the GFS and the nam are in pretty good agreement . Cape over 3000 , TD in the upper 60's and a nice bulge in the dryline. Look's like another chase close to home .

 

[Mikey Gribble]

Yeah I just checked out the 00Z NAM so you can scratch off a lot of my concern from my blog post this morning.

This morning I was wondering about what would serve as a focus for convection because the moisture gradient on the dryline wasn't tight and too far west, but there was a sharp kink in the isobars that almost looked like a surface low by the way it wrapped moisture around it.
Well now in the 00Z run that kink in the isobars is a surface low and the dryline is sharpened up and much farther east. As a result the NAM fires off convection in this area when it wasn't this morning.

This going to be a tough one to call. You have a great theta e tounge wrapping north around the small surface low through the afternoon. Dewpoints should be in the mid to upper 60's. It looks like any morning convection will clear out allowing for good insolation as temps climb into the 90's. With excellent directional shear (180 of turning, don't see that very often) and deep layer shear in the 50kt area, this should be a very favorable environment for tornadic supercells over a somewhat small area.

My worries are LCL heights. Upper 60td'd is all you can hope for, but you are still looking at a 20 plus degree spread and I just looked at the ML LCL map over the target area and even though you can't see much detail on WXcaster, it looked like LCL's will be quite high until late afternoon when temperatures begin to fall. That may be a serious problem. I'll have to start pulling forecast soundings in the morning to figure that one out. Other than that the setup looks pretty good.

 

[Bill Tabor]

Looking at this mornings NAM/WRF run tomorrow looks concerning particularly in the TX region where I see 10 to 12 degree temps at 700mb - apparently not really eroding much during the day. With no shortwave to kick things off we will rely solely on daytime heating and convective temperature. Additionally, appears there may be some ice crystals higher up in the atmosphere - overspreading cirrus - another concern? Also 500mb temps are showing only around -10 - so lapse rates may be a bit poor. Cape should be high, but with CINH looks like a bit of a roll of the dice at this point.

 

[Ryan Pfannkuch]

Sitting here pondering my first Southern Plains chase opportunity of '09. After tooling around KS several times in March/early April on those high shear/low CAPE setups, at the very least I am looking forward to finally having a chase day with legitimate Td's into mid-60s territory or better.

Honestly, this morning's 12z model suite was the first close look I have taken at tomorrow's setup, so I don't have a good feel for trend. As Bill mentioned, the cap and lack of more robust synoptic forcing appears to be an issue, with the 12z NAM/WRF Wichita Falls sounding valid 0z Wed depicting 78 J/kg SBCINH, and Graham TX 46 J/kg. Hopefully there's a nice OFB floating around from the daytime convection to the north, or this could be a long scenic drive, with only big hailers north of the boundary mainly in OK.

On the positive side the shear/hodo looks quite enticing...noting the 50+ kt deep layer shear, and nice loopy look in the low levels. Nice to not see a blatant "S" shaped hodo with this setup. Hopefully something can go and take advantage of this environment.

Based on my first glance, my 4-county target area along the WF in north TX would be: Baylor, Archer, Throckmorton, Young

 

[Jared Farrer]

Yeah I was going to make the trip but decided to sit this one out. I live pretty far away from that area.

Main thing is strong thick cape pretty much until 0z. The NAM and GFS both show a dryline bulge but will there be enough convergence. The NAM does hold off convection until 0z and only then it shows a small QPF around Abilene. Thing is with storm motions being slower it would take time for a storm moving off the dryline into the better shear/instability closer to the warm front. And all this before nightfall.

However, with 2000-2500 j/kg at 0z and steep low level lapse rates (dry) explosive development could take place. And with the shear being amazing, wow! Backing winds near the surface to veering slightly through the mid-levels to wnw upper levels, hodographs are impressive. And with 40-50 kts bulk shear storm motions would be nice!

Not hard to see some major wedge potential. It looks like a very impressive enviroment! But looks like it wont be in place until late in the period with a small window before nightfall.

Even if for some reason their are no tubes, with that kind of a set-up their could be some great photo-ops. Even if it is just after nighfall. Think about a flying saucer just after nightfall illuminated be lighning, wow! With that kind of setup could be some really structurific stuff. But with the shear and somewhat higher precipitable water things might transition to HP pretty quickly, ...........maybe.

-Jared

 

[Brad Nelson]

I'm thinking this is certainly a Boom or Bust day as we have a very unstable airmass with SBCAPE on the order of 2,000-3,000 j/kb from this morning’s model runs, most instability forecast off the GFS. MLCAPE values up around 1500-2500 j/kg with some higher bullseyes. I checked out some of the forecast soundings off Bufkit and convective temps look to be in the 90’s so there will have to be some stronger forcing to get things to go tomorrow. One thing to make note, if you buy into it all that much, is the 4km WRF does not break out precip south of the Red River and does keep it capped off. The killer looks to be the extremely warm layer between 800 mb and 750 mb, even warmer than noted at 700 mb. Further south near Abilene could have promise if the dryline does indeed bulge and lead to stronger low level convergence/forcing. The NAM and GFS break the cap in the Abilene forecast sounding for tomorrow but with very high LCL’s forecast. Helicity values are impressive here though. Could these storms break the cap down near Abilene and then slowly progress towards the Graham area by early evening with lowering LCL heights and increasing low level shear profiles? Very slow forecast storm motions as well and very chaseable. Then you have to consider development near the triple point of the low, dryline and warm front east of Lubbock and how the warm front and morning outflow boundary play into the picture across northern TX. Difficult at this point to choose a target but I’m sure things will get sorted out some after what happens with tonight’s expected MCS and where we see these features set up tomorrow.

 

[Mike Hollingshead]

Nice to see the SPC note the whole venting into the inflow region issue you get when you have to much turning. I'm a big hater on those types of setups, where you are near or over 180 degrees. Just never seems able to work, at least for very long...and it makes perfect sense. I'd hope for a very deviant storm tomorrow and figure better chance of that might be a storm out on the dryline. But yeah LCLs might be an issue out there. Further east, given a storm, I bet it behaves like one last year in that same area. I think it formed west of Wichita Falls, had a great hook for a while, then slowly died...while having great structure as it did so(frequently happens as updraft stops producing a core). Not sure the exact day or even 100% sure that was last year and not 07, but that's the storm behaviour I would expect tomorrow along any ofb or warm front. (yeah it was April 7, 2008)

There, now anyone chasing can bank on long lived cyclical tornadic sups in nc TX.

 

[Shane Adams]

There, now anyone chasing can bank on long lived cyclical tornadic sups in nc TX.

If you can get one to form....I'm not liking the h7 temp forecast at all.

 

[Paul Redmond]

Nice to see the SPC note the whole venting into the inflow region issue you get when you have to much turning. I'm a big hater on those types of setups, where you are near or over 180 degrees. Just never seems able to work, at least for very long...and it makes perfect sense. I'd hope for a very deviant storm tomorrow and figure better chance of that might be a storm out on the dryline. But yeah LCLs might be an issue out there. Further east, given a storm, I bet it behaves like one last year in that same area. I think it formed west of Wichita Falls, had a great hook for a while, then slowly died...while having great structure as it did so(frequently happens as updraft stops producing a core). Not sure the exact day or even 100% sure that was last year and not 07, but that's the storm behaviour I would expect tomorrow along any ofb or warm front. (yeah it was April 7, 2008)

There, now anyone chasing can bank on long lived cyclical tornadic sups in nc TX.

Your reminding me of Jacks County in 4/03/08. Similar setup. It looked so promising with wall clouds but never seemed to get its act together.

 

[Jared Farrer]

Most recent runs look like the show shifted west and south a little more? LOL. Well Cap is now stronger for the most part and the NAM now has it with no precip not even along the warm front really. LCLs are a little bit weird but I dont think they are bad enough to warrent not chasing. But the Cap is for sure! EHIs have increased right where the cap is strongest, LOL. Its just ugly. Things could change again, just too far away for me.

Mike has a point, to much turning in the upper levels. Even more so than 4/7/08. So seeding(so to speak) is a question. Be interesting to see what happens.

I do think though that if anything where to get going, being on it early would be the key. Good photo ops could be abroad!

 

[Greg McLaughlin]

I'm not writing this one off just yet. I have seen days that have looked great the day before, but instead turned to junk. It will be interesting to see if the cap can be broken tomorrow down around the same area many of us chased Friday. There is a lot of surface convergence forecast in that area, but I am not sure if that will be enough to get through that fat nose on the forecast soundings. I have a great job for chasing so I will be there.