10/5/08 FCST: KS/OK/TX

[Andrew Ryan]

The moisture and instability has greatly increased in the last couple of model runs. But the wind fields are starting to concern me. It looks for the most part the best thermos are overlayed with speed shear only. I hope this changes in future model runs.

But either way, there should be some severe weather and I will be happy with that!

 

[Michael O'Keeffe]

The latest surface obs are looking good moisture wise with upper 50's tds all over OK with low 50s into Kansas already and with southerly flow for the next two days I think the moisture issue won't be a big deal. We will see but as of now the TX Panhandle could erupt.

 

[Mike Hollingshead]

Monday officially stinks now in my book(now that the NAM fully sees it and mostly agrees with the GFS). Looks a bit like a classic rainy day. Never see anything good off those country wide stalled fronts directly under the upper low. And also hard to think of many good things off a weakening system(low levels are especially toast by Monday afternoon). My only "hope" I think is hoping for some clearing near the upper low center, but it doesn't even appear to be terribly cold anyway. The 850mb winds right ahead of the mid-level vort max are kind of interesting, but, any sort of clearing may be rather hard to come by there.

I think the best hope is the system behind it for late next week. Looks like that one wants to bring winter on down.

 

[Andrew Ryan]

I still believe that Sunday can be a solid chase day. With the dramatic increase of moisture today, I have little doubt that 50+ dewpoints will be in place on Sunday.
http://hoot.metr.ou.edu/surface/obs/spl

The NAM without a doubt has a much better scenario than the GFS. The NAM has sets up a pretty good scenario for supercells in the panhandle of TX/OK and into parts of extreme SW KS. The forecast soundings for this area looks to be favorable for supercells around 0z. This could become problematic with the days getting shorter.

http://beta.wxcaster.com/cgi-bin/parse_skewt_trace_all.cgi?model=NAM& STATIONID=KAMA

My only concern right now is instability is on the low side and cold temperatures are a bit lacking in the upper levels. Hopefully, things will become more clear as we go through the day tomorrow.

 

[Chris Lott]

I think Sunday looks good mainly for the Texas and Oklahoma panhandles. Models do show moisture making it back up that far, but some forecast soundings I have checked out don't show much as far as CAPE. Wind shear looks good but I think this will start with a few cells blowing up the Texas/Oklahoma panhandles and turning linear as it moves east. Just going out on a limb here, if I were to make a "box" for potential severe in the Texas panhandle right now, I would go from Childress to Dimmitt to Dalhart to Canadian. I think anywhere in that area has a good chance of seeing severe weather on Sunday. I made a goof on my part. I originally had Monday posted and meant Sunday.

 

[Brett Roberts]

It seems clear that the primary inhibiting factor on the models, at present, is ongoing convection throughout the day Sunday over the area of interest. The 60-65 F dew points progged by the NAM throughout the TX/OK Panhandles seem more than sufficient for moderate instability at first glance, particularly given the mixing ratios that yields at 2000-3000 ft. elevation. But CAPE values are depicted as mainly < 1000 J/kg, because temperatures are held in check by the cloud cover and precipitation. If this situation were to change, the dynamic side of this system looks fairly interesting, with ample speed and directional shear. Given the time of year, it would be quite a shame to see a slam-dunk supercell day on the Caprock - and possible tornado day - go to waste because of a lack of insolation. On the bright side, the ECMWF from earlier today is suggesting another major western U.S. trough could be poised to move into the Plains by next weekend.

 

[Mike Hollingshead]

The 6th is Monday. Sunday is probably the more deserving of a thread by now though. I keep getting confused on a few posts, lol. I'm like, how is the TX panhandle going to erupt on Monday.

 

[Chris Nuttall]

MOD NOTE: Since that vast majority of this discussion has shifted to Sunday, I'm going to change the thread title, date, and region to match.

 

[Angie Norris]

I'm thinking Childress would be somewhere nice to be tomorrow evening. There looks to be a bit of a CAPE spike by 0Z...granted, it's progged at only about 1000J/kg, but this isn't May, and 1000J/kg can be enough in early spring or in the fall to make things interesting. There is a nice theta-E spike as well. The winds are bit too unidirectional for my liking, but speed shear is decent. The major limiting factor to instability will be ongoing cloudiness, and I'm thinking we'll see a MCS develop.

 

[Bill Schintler]

Chase Target for Sunday, October 5

Chase target: 20 miles south of Childress, TX.

Timing and storm mode:
Elevated convection will be ongoing in the TX panhandle early in the period, and will become increasingly surface-based as it expands towards the east. Storms should reach the target area between 3 and 4 PM CDT. A few supercell storms along with an isolated tornado or two cannot be ruled out for any storms that can become surface or nearly surface based.

Synopsis:
Big changes are taking place in the synoptic pattern. The persistent Hudson Bay upper-level low is finally showing signs of breaking down and moving east. Further west, a trough was digging southeast and becoming increasingly negatively tilted with a 50m, 12 hour H5 height fall bull’s eye centered over the Four Corners region. Between these two features, a shortwave ridge over the Upper-Midwest was inching eastward. Convection has fired in the TX panhandle courtesy of a lead H5 wave and some attendant isentropic up glide along the 310K surface.

Discussion:
Regarding model guidance; the WRF, GFS, UKMET, SREF, and NGM were investigated. The NGM is an outlier and is too progressive with forcing and eastward progression of QPF. Recent model runs are more pessimistic with surface-based instability. During the day, widespread CI over western TX will inhibit insolation over most of western TX and the panhandle.

A cold front of Pacific origin will enter the western TX panhandle during the afternoon, while further east a meso-scale low will organize in the Turkey, TX area. Marginal BL moisture is noted, with SFC dewpoints generally AOB 60 degrees. Lapse rates will be poor as the colder temperatures aloft will lag the trough axis. Limited instability will result, with MLCAPEs between 500 and 1000J/kg beneath modest mid-level lapse rates of 5.5-6 C/km. Low-level flow will locally back in the Red River area, enhancing low-level hodographs and moisture pooling. SFC-3km SRH will locally increase to at least 300m2/s2 as a southerly LLJ strengthens to 50 kts between 00Z and 03Z. Deep-layer shear will increase to 50 kts as an increasingly negatively tilted H5 trough shifts east into the area.

- bill
10:11 PM CDT, 10/04/08