4/18/09 FCST: KS/OK/TX

[Jason Bolt]

Saw the SPC day 2 has a 30% area and mention of tornadoes tomorrow for NC OK and SC KS. I am probably the most amateur of amateur forecasters on here, but if I am reading the WRF correctly, T/Tds in the I-35 corridor at KS/OK border will be 65/55ish by noon tomorrow w/ 500-750 CAPE values in that area. I am just learning to forecast instead of simply following SPC, but I see enough to interest me given its a weekend, close to home, and I am looking for something to do tomorrow. I expect I will head out in the morning for Blackwell or Wellington and adjust on the way.

Feel free to jump in and tell this newbie why I will be wasting gas tomorrow!

 

[Chad Cowan]

The thermodynamics are going to be solid under the cold core (~-20C 500mb) but the awful wind profile from around 700mb down to the surface should mitigate most of the tornado threat. There should be some decent storms around the Wichita area but large hail will be the main threat. There might be a brief tornado possible IF surface winds can get up to 10kts (maybe if a secondary low develops??) or if a storm can latch on to a residual boundary which would increase low level shear. Even then, as has been the case with EVERY system thus far, marginal moisture will a limiting factor.

 

[Michael O'Keeffe]

I am looking at the NW Missouri area based on the 12z NAM, better moisture and some sort of wind shift line should be present. The 4km WRF precip is breaking out a few nice supercells near the I35 corridor from KC to Lamoni, IA. As far as tornado potential is concerned it is pretty limited, but ya never know. It looks like one of those setups where you have to wait til the morning to see what is actually going to happen.

 

[Brandon McClung]

This day does look interesting. Looking at the 12z NAM, it has 0-3km CAPE maxed out in the region (250 J/kg) , with 0-3km LRs at 8-9 K/km, below steep midlevel lapse rates at 7-8 K/km. With the cold 500mb temps, at -22 to -24C, and warm moist air below, it shouldn't take much to get a storm. Both the NAM and GFS show a nice dry slot entering the area in the wake of the morning convection/precip that will probably start tonight and continue overnight. The NAM doesn't do as well of a job as the GFS in defining a surface boundary to increase surface vorticity. The GFS has stout convergence along the boundary oriented N-S right along I-35 while the NAM has a more SW-NE oriented boundary along I-44, with slightly weaker convergence. The storm motions with the system should make the storms chaseable as the NAM showed 20 kt storm motions.

If you could put yourself where the sfc vorticity and 0-3 CAPE coincide, you should see some interesting things. Given the extremely cold temps aloft, the chances for hail are very good. I would set up near I-35 in a Perry, Enid, Blackwell triangle for now.

 

[Jeff Snyder]

Haven't looked at much, so I won't make an in-depth forecast of any magnitude. However, I did just glance at some forecast soundings from the 00z NAM, and many soundings / hodographs show significant counter-clockwise curvature to the tropospheric wind profiles. For example, check out THIS time-sensitive forecast sounding valid tomorrow evening at Tulsa, OK. The weak low-level wind field is obvious, but it creates significant counterclockwise curvature that seems very support of anticyclonic / left-moving supercells. Not much 0-1km SRH, but there does appear to be some appreciable negative 1-3 km SRH. In fact, it certainly looks like anticyclonic supercells would be preferred over cyclonic supercells in much of the OK/KS border area. I haven't found any website graphics that display SRH < 0, nor any that show SRH for a left-moving supercell. As such, it's hard to get a quantitative handle on SRH for a left-moving supercell tomorrow. However, the hodograph would seem to support enough SRH and deep-layer shear for chaseable anticyclonic supercells under -18 to -22 C 500 mb temps that yield >1250 j/kg CAPE.

 

[Jonathan Whitehead]

Am I the only one seeing the dryline bulge in NW TX on the 00Z run? Models have 60 dews up to the red river with sufficient SBCAPE on the order of 1000J/kg. Helicity will be the issue but the NAM (as SPC has pointed) is showing 40-50kt midlevel SWLY jet right overhead the Red River valley. Its a little bit similar to the Gainsville day of a few weeks ago but with a few differences, mainly degree of instability/helicity. If I do recall correctly instability was about 2000 with helicity of 200. Parameters wont be that high but they will be sufficient. Using Jeffs link, I edited it for ADM and GLE and got a somewhat similar profile as up north, granted moisture is better at the sfc, however, it is rather shallow, esp on the ADM sounding so mixing would be an issue. The hodographs are sufficiently curved to generate some rotating storms if storms can be realized.
I guess the main question for tomorrow is if we can get enough heating and convergence along the dryline as well as deep enough moisture to prevent mixing.
You can see why SPC is going SLT tomorrow b/c everything extremely conditional. Will wait till morning when I can see hard data before making a final decision.

I know everyones interested in the cold core setup up north but Id much prefer the warm sector any day over cold core.

 

[Jeff House]

Another plus for NW Texas will be a secondary warm front pushing north from South Texas. This boundary marks the leading edge of the more marine influenced air that stayed in South Texas Friday. Assuming the front makes it into North Texas by Saturday afternoon, it could create a nice intersecting boundary with the dryline. Also some marine air would help a bit with the moisture. Weak wind fields up to 850 are an issue, but intersecting boundaries have a way of creating sufficient helicity.

Edit: MCS in progress this morning in central/south Texas will keep very moist marine air and second warm front in South Texas, but dews have made it to 60 in NW TX anyway. Jet streak moving from SW to central Texas promoting morning MCS. Vapor shows second jet streak on AZ/NM border that could trigger NW TX later this afternoon.

Maybe it is not an ideal setup but, on the weekend why not try? Good luck to all in both/all areas.

 

[Darren Stephens]

Wow..the latest SPC Day 1 has moved the risk area way more east than it was yesterday. If we can get a break in the clouds and get some surface heating we could see some nice storms here in Oklahoma later.

 

[Jason Bolt]

Currently headed for Wellington, KS. SPC has added a 5% tornado prob and a hatched area for hail in KS/OK border region. Still don't think this will be a great day, but its something to do.