3/8/10 FCST: OK / KS / TX

[Brian Stertz]

Looks like the 12z NAM has a small window of opportunity across WC OK tomorrow between about 5-9pm. Good lcl's...strong vorticity (0-3km vgp's .4+)...favorable lapse rates... eff. shear 30-40 kts.and even a little extra convergence from a slight dryline bow. Although the T-Td spreads are not too exciting, the wave moving into W. Oklahoma is pretty strong so all bets off. Enough there for a few low topped supercells...if NAM holds true. Question is can the stuff get mean before sun sets...

Target right now would be Sayre OK.

 

[Bill Schintler]

Chase Target for Monday, March 8

Chase target:
Roll, OK (30 miles northwest of Elk City).

Timing and storm mode:
Non-severe storms will be ongoing over the area through the early afternoon hours. Partial clearing will then take place over western OK after 3 PM, and a few discrete storms should fire in the target area between 4 and 5 PM, CST. Most storms should remain below severe limits; however, a brief, weak tornado or two cannot be ruled out. Storm motion will be towards the northeast at 35 mph.

Synopsis:
UA analysis indicated a closed H5 low over SRN CA/AZ; with 12hr height falls concentrated over SERN AZ. A second, weakening circulation was located over IA. An axis of 55F SFC dewpoints had worked into the TX panhandle in a region of SERLY SFC flow. Further W in ERN NM, clusters of mainly elevated storms were ongoing in a zone of WAA and large-scale assent.

Discussion:
Elevated convection will be widespread during the morning hours, with partial clearing taking place from southwest to northeast through late morning. Storms should redevelop near the triple point of an advancing DL/Pacific CF and the retreating WF, southeast of the SFC low over the OK panhandle. Significant SFC-3km SRH in excess of 300m2/s2 will exist well NE of the WF, with the largest hodographs remaining well E of the axis of modest instability. SFC-6km shear will also decrease throughout the afternoon with the approach of the ULVL system, however SFC-1km hodographs will increase after 00Z as the BL decouples and a southwesterly LLJ increases to 40-45 kts.

Instability remains the primary limiting factor for storm intensity, with MUCAPE’s AOB 700 J/kG. Mid-level lapse rates will increase later in the afternoon to 8-9 C/km in the H7-H5 layer as the cold core low approaches from the W; however, the steepest lapse rates will remain well NW of the retreating moisture axis.

- Bill
KD0DJG
www.twistertoursusa.com
9:57 PM CDT, 03/07/09

 

[Jason Boggs]

Well, it appears that I will be chasing on Monday. Right now, my initial target area is Canadian, TX. I'm really not looking for much in the way of severe weather, but some marginally severe hail along with a possible weak, short lived tornado is possible near the surface low. Really, I'm just going out to get back in the groove and check out the equipment for the meat and potatoes part of the severe wx season.

The low that is progged to initiate the thunderstorms will pretty much be right over the Panhandle on Monday afternoon. 500mb temps will be very cold which will help contribute to steep lapse rates. Surface CAPE on the other hand will be very marginal at best. CAPE values may approach 800 j/kg, but cool surface temps in the upper 50's and cloud cover may keep it from reaching above 500j/kg. Td will be in the upper 40's and low 50's in the region which really isn't that bad for this time of year.

Maybe I can at least get into some severe hail and gusty winds, but right now I'd settle for a few Cg's and towering Cu.

INITIAL TARGET AREA: CANADIAN, TX

 

[cedwards]

I will target Roll, OK today. The clearing should reach there earlier than I expected. I am not overly optimistic about today, but it will be nice to go out and see some convection and test out the equipment.

 

[Jeff Snyder]

Tough call... The past couple of days, the model runs weren't doing much of anything for me. The forecast hodographs were very S-shaped, and instability was forecast to be nearly nil. However, the 9z SREF and 12z NAM look a bit more enticing, with more straight-line hodographs and better instability (still weak, but better). The latter, I assume, is the result of sfc temps being a bit warmer than the previous forecasts were indicating. Regardless, looking at the 12z WRF forecast soundings and 9z SREF products, there looks to be an interesting zone from NW OK arcing a bit southeastward than southward towards the area between Lawton and Altus (N of some potential dryline/pac front bulge on the NAM). In this "band", forecast hodos look alright, and instability may be sufficient for a robust updraft. I have a little concern with there perhaps being only weak shear between ~1-5 km, but the near-surface helicity may be respectable if we can get a right-moving supercell.

I'm biasing a bit towards the south since vis sat data indicate that southwestern OK may see insolation before northwestern OK. Surface obs indicate Tds in the 54-55F range in southwestern OK, with 58-59 Tds not too far south into TX (e.g. 57 at CDS, 57-60F just south and southeast of there). These higher Tds shouldn't have too much of a problem getting to at least southwestern OK, if not westcentral OK.