11/10/08 FCST: OK/TX/LA/AR

[Heidi Farrar]

The SPC has highlighted a day-3 30% hatched area for east Texas and no ST forecast thread yet?! The NAM and GFS are in good agreement on just about everything: 70-degree temps all the way to the Red River by 00Z; 60-70-degree dewpoints from the Red River to the Gulf Coast; ssw 850mb winds ~40-50kt, westerly 500mb ~60 kt... There's also a pretty big area of CAPE in the 1500-2000J/kg range from southeast into central TX, with ~500 stretching all the way into west-central OK. However, it also looks like the best CAPE will remain south and west of the best shear. In addition, the models are showing precip breaking out very early, so one wonders if the destabilization necessary for a more widespread severe event would even occur. I guess I am a little surprised to see a hatched area with that limiting factor, especially one so large. But it's still a very interesting setup.

 

[Brandon Lawson]

I think early convection is going to be the biggest problem with this setup as the massive trough ejects too early. That's going to limit a lot of the instability. Veering 850 winds won't help either, but it's worth keeping an eye on. It seems like it always comes down to hoping that the models will slow the system down a bit. Tonight's GFS run actually looks a lot better, with increased directional and speed shear. The surface low is still rather pathetic, but I guess that is partly due from having a weak trough.

Strange how Sunday could have been an amazing day if there could have been any moisture and instability, and then on Monday the convection starts too soon when the moisture is available. Hooray.

 

[Michael O'Keeffe]

Looking at the 12z WRF the models have really changed and it now appears as though a significant severe weather event can unfold over C Texas. A sharp dryline looks to extend from the Red River south into Mexico and 60F+ tds will poke all the way into far SW Oklahoma. A warm front looks to be draped across NW Texas into NC Texas down into EC Texas. A strong southerly LLJ and very strong SW 500s, along with perfect SE surface winds will create great shear profiles all along the dryline. The triple point appears to shape up near Childress, TX.

With all of this in place, IF the 12z WRF verifies and if the rain doesn't ruin the day we could see a significant severe weather outbreak across central Texas. Jeez I wish I could chase this event. I'm jealous!!

 

[Chad Cowan]

Would-be-Target: Brownwood, TX (100 mi sw DFW) @ noon

Compact shortwave trough currently over AZ will take on a slightly negative tilt and phase with the sub-tropical jet early in the fcst period. Lift/divergence will be enhanced downstream of the phasing. This will result in elevated convection during the overnight hours into early morning over the target area. Even with the possibly remnant overcast skies, instability will be sufficient for supercells owing largely to a very moist airmass. Main concern right now is too much forcing and not enough cap to hold off convection until peak heating and to also keep cells discrete. H5 speed max is currently rounding the base of the shortwave and will be over the target area around noon when sfc based convection will develop along the dryline. Slightly veered H85 winds should not be a problem due to the se'rly sfc windfield which will enlarge low-level hodographs. Tornadoes are possible in the Texas target area and an isolated strong tornado cannot be ruled out in the northern half near the baroclinic zone due to the low LCL's, high shear, and moderate instability in this area especially if low clouds can mix out early. Early-mid day elevated convection ne of the sfc low will be capable of large hail. Climatology and pattern recognition suggest that a significant severe event is possible tomorrow, but mesoscale features need to be nailed down before where and if this will be realized.

 

[Michael O'Keeffe]

The 12z WRF doesn't look bad at all especially along the warm front and east of the dryline from Abliene to Brownwood. The precip models are also showing what appears to be a supercell riding the warm front E of Abilene. The visibile satellite isn't showing too much cloud cover west of Brownwood to Wichita Falls line. CAPE already appears to be poking into West Texas and I would think it would only get better as the dryline moves eastward mxing out those low clouds. The 12z WRF also shows 1000-1500 j/kg of CAPE in W/C Texas as well. By the looks of it now that could verify.

The RUC however paints an ugly picture with no CAPE and lots of precip.

If I could chase today I still probably would targeting somehwere east of Abilene along I20 and adjusting from there. Good luck to all that do chase today.

 

[Verne Carlson]

Heads up for a cold core setup in the panhandles today. The positioning of the upper low and the surface low are almost vertically stacked but they may be positioned far enough away from each other to give a CC setup. The other ingredient, cold 500h temps are certainly there.

If I were out chasing today I'd be in Guymon, OK looking for that 'string of pearls' to develop.

Edit: nice surface heating going on around Amarillo this morning. Steep lapse rates and enough low level cape could make for a few CC tornadoes later today.

 

[Mike Johnston]

Looks like the RUC is under-doing surface dewpoints by 2-3 td, based on comparison of some actual obs over central TX, compared to the 17ooz forecast. Vis satellite also shows some decent clearing patches just along and to the west of the theta-e ridge. Still like the shear profiles over the area and wouldn't be surprised to see a watch out over the next hour or two.

 

[Bill Schintler]

Chase Target for today, November 10

Chase target:
10 miles east of Altus, OK.

Timing and storm mode:
Supercell storms should fire by 1 PM CST, and move to the east and northeast at nearly 40 mph. Bridge options over the Red River are limited, so it is advisable to position on the north side of the river.

Discussion:
SFC analysis indicates low pressure centered over NERN NM, with an occluded front extending S and E to a triple point north of CDS. A nearly stationary WF extended E along the Red River while the CF and DL extended S and SW along a CDS to LBB to MAF line in TX.

While SVR WX should occur over a wide area this afternoon, perhaps the optimum location will be along and immediately N of the WF near the triple point. Visibility of storm structure should be best in this area as opposed to areas further south with widespread LLVL cloudiness. An axis of 55-60F dewpoints is nosing N towards the area, while clearing has taken place in the TX panhandle which will allow for insolation. Latest visible satellite trends indicate a band of enhanced CU extending from DYS N to CSM. The RUC and SREF appear to have a good handle on LLVL moisture. Despite the moderate SFC moisture, weak mid-level lapse rates will reduce attainable instability, with MLCAPEs strugging to reach 500J/kg. Subsidence should persist for the next few hours until a second wave approaches from the SW. The strongest LLVL directional shear will shift slowly east with the LLJ; however, SFC-3km SRH’s to 300J/kg should exist. SFC-5km Deep-layer shear in excess of 60 kts will also aid in storm organization.

- bill KD0DJG
12:12 PM CST, 11/10/08