3/4/11 FCST: W OK/TX/KS

[Donovan Gruner]

Well, looks like we could have another good chase day towards the end of the week. Although it appears dewpoints may be on the low side (low to mid 50's) everything else is looking quite impressive. 12z NAM shows an area 1500+ j/kg, with textbook curved hodographs over Western Oklahoma. EHI also up around 3.00 in the same area. Hopefully we can get some better moisture in subsequent model runs. If so, it appears this could be the first major plains event of the year.

 

[Verne Carlson]

I'm liking the cold core dynamics up into w KS with 500h temps down to -35c and a compact little surface low. 50 Tds could get the job done. PTO day already put it for.

 

[Skip Talbot]

I'm liking the cold core dynamics up into w KS with 500h temps down to -35c and a compact little surface low. 50 Tds could get the job done. PTO day already put it for.

Not seeing those -35C temps over KS, Verne. Which model/run are you looking at? Seeing temps more along the lines of -20C with surface dewpoints low to mid 40's along the portion of the setup that would be more cold core like on the GFS and NAM. Still though, I agree this is the area I would watch most closely for tornadoes. Those numbers are still enough to crank out some tornadic minisups. You'll have to catch NNE moving cells as they cross what looks to be a fairly sharp warm front. That enhanced directional shear along the front and steep lapse rates from the surface heating south of the warmfront and cold air aloft could be enough for cells to crank off a tornado or two before they move into more stable air to the north.

Western OK has an absolutely beautiful little trough and veering wind profile forecast at 84 hours. The moisture is going to be a problem though. While 50's dewpoints are enough for the high terrain, the LCL's look like they are going to be quite high: 2000m or so. That's going to cut into the tornado potential. The cap looks manageable, if not ideal on the NAM, with a strong morning cap suppressing morning convention and eroding by late afternoon to let some storms fire off. GFS has a bit more stout, so we'll have to see which one pans out to determine or initiation potential. Given the decent instability, modest, moisture, and great veering wind profile, I'd expect a few high based LP supercells over the western OK/TX border. I would look further north to the warmfront/quasi-cold core for the better tornado potential, but storms in western OK could be very photogenic.

This setup looks like it could be a nice chase event over great terrain with a shot at a minisup tornado up north or a photogenic LP down south. Severe threat will be rather conditional, however, dependent on moisture advecting in time and the finer details of how strong the cap is going to be.

 

[Matthew Piechota]

If this somehow were to pull better moisture up if would have some pretty darn good potential but just not seeing that right now. It's a really nice looking sfc low/warm front with the even better looking s/w trof. You have some really nice looking wind profiles/hodos just to the east of the sfc low and looking at the H7 RH fields at 84hrs, it's trying to break out convection from southwest KS on southward through southwest OK/northern TX. And with the jet coming through at 0z to western OK I would think that would help get convection to pop. I'd be curious to see what the NAM would do the next day as well.

 

[David Reimer]

I just started really paying attention to Friday this morning when the NAM came into range. The 12Z NAM looked rather favorable for supercells across portions of the warm sector (Texas/Oklahoma) by Friday Evening. Just glancing at the 18Z NAM, it's backed off considerably and more in line with the GFS for the lower level wind fields. Still its a few days out so there's no reason to go model hugging run to run at this point. I wrote up a discussion over on the website earlier this afternoon where I discuss my thoughts more in depth. I do agree that Friday looks more like a 'structure photograph' day instead of a tornado day due to the lower moisture amounts in the warm sector, but I have not really taken an in-depth look at a possible cold core solution like Verne posted about, I'll have to take a look.

My discussion can be read at http://www.texasstormchasers.com/2011/03/01/back-to-oklahoma-for-friday/

 

[Verne Carlson]

Well it now looks like the cold front pushes the best moisture south of the upper air forcing. EHI values are way down over previous runs of the NAM. This one looks like it will be in the eastern OK jungle. Maybe something will go near Ardmore, OK but will move east into unfavorable terrain quickly.

 

[David Douglas]

Verne - Agree. This system just blew apart between the NAM/GFS runs yesterday and the current 6Z runs. Yesterday there was a well defined low/triple point in SW Kansas @ 0z. Today, it's much weaker and further south near Wichita Falls and earlier in the day @ 18Z. Very little instability, EHI, and low Td (50s).

 

[Skip Talbot]

I can't believe how much the models shifted on this setup. Last night's 0z NAM completely threw away the surface pattern that had been consistently showing on the last three runs of the NAM and GFS. I didn't even recognize it at first when I first pulled it up. The 12z run is showing pretty much the same. The nice low over the panhandles is now a weak elongated area of low pressure spread out over the eastern plains/midwest. That will ruin the low level shear, which is the one really nice thing this setup had going for it. Now we are left with meager dewpoints further east where the terrain is not only more difficult for chasing, but also lower in elevation making those dewpoints even more marginal relative to the high plains. With veered surface winds, marginal moisture and instability, I don't see much of a chase here at all except for maybe the locals of NC/NE TX, E OK, AR/MO who want a shot at some isolated severe hail/wind amongst clusters of otherwise generic thunderstorms. Maybe we the models will completely flip again and we'll be back in business. What a roller coaster.

 

[Donovan Gruner]

I was confused starting with the 18z run yesterday, thinking my computer wasn't loading the right thing or something. It's unbelievable how much it changed. Like you said Skip, the area of low pressure is an absolute mess on the new runs. I'm amazed at how disorganized everything looks all of the sudden. There is a pocket of so-so CAPE in SC OK and NC TX, but almost no helicity to speak of. I'm still hoping for another model flip though. If Friday doesn't pan out, we always have Tuesday to look towards... although the new runs are pushing that a bit far east for my liking.

 

[RMacDonald]

Just pushed out 05Z SmartModel forecast for the 4th. Still only seeing a slight potential at best for regions of E. OK through Arkansas. It was even a struggle to find data to support this area. Any additional thoughts?