Chase Log: September 14th, 2005
Click on any of the SPC products below (Convective Outlooks, Watches, or MCDs) to see the SPC's "Severe Thunderstorm Events" page pertaining to this event.
Total Distance: 420 miles
Target Area: Quanah, TX
Chase Area: Crowell, TX, to Frederick, OK
Maximum SPC Risk category: Moderate
Watches:
Tornado Watch 790, Severe Watch 791
Mesoscale Discussions (MCDs): 2200, 2201, 2204, 2205, 2206, and 2207
A good Fall outbreak -- could it be?! Finally, strong mid and upper-level flow was progged to cover portions of western Texas and Oklahoma as a cold front became stationary from west-central Texas northeastward near I-44 in Oklahoma. Clear skies developed behind the front by mid-morning, and models were forecasting significant instability along and immediately behind the stationary front by late afternoon. In addition, several outflow boundaries were located throughout the area courtesy of overnight and morning convection. This looked to be a classic case of strong instability on the cool-side of a good baroclinic boundary. Easterly flow behind the front created very strong shear by afternoon as well. In fact, RUC mesoanalysis showed 250-500 m2/s2 0-3km SRH and 50-90kts effective deep-layer shear! While the environment looked primed for tornadoes, storm mode became the downfall of this event.
Gabe Garfield, Dan Dawson, and I chased the western north TX / southwestern OK storms today. From a parameter / index standpoint, I was optimistic about the chance of tornadoes, and even the possibility of a significant tornado given the very strong low-level shear along and immediately north/west of the front (300-500 0-3km SRH), combined with the very strong deep-layer shear (50-90kts) and moderate instability (3000-4000 sbCAPE). We sat down in Altus for a while, while storms developed west of Paducah. Seeing no real signs of agitated Cu north of the Red River, we opted to head south to Quanah. Surface obs showed higher T-Tds and higher LCLs to the south of the Red River, so we knew we didn't want to get too far into TX. Seeing no other storms nearby, and given the northeast motion of the storm cluster, we opted to head south to Crowell. By this time, the storms that were originally near Dickens/Guthrie/Paducah had congealed into an MCS-like convective mess. So, we checked radar in Crowell, and noticed a couple of more discrete storms near and north of Childress. Decision time... Head north to get into the awesome shear environment along and north of the Red River, or head east / south to try for a 'tail-end charlie' with the convective mess to our west and southwest. Given the bow echo shape of the convection to our southwest, and the seemingly favorable environment to the north, we headed back north out of Crowell to Quanah. There was a pretty nice supercell with decent mesocyclone near CDS, moving east-northeast. Unfortunately, convection was pressing northeastward to the east of this storm, which we knew would result in the demise of the CDS storm.
We ended up meandering to Vernon and north ot Frederick, all while hoping the quasi-linear storm mode would give in and give us at least one discrete supercell. Alas, this was not to be. We ate at a Chili's in Lawton before heading back to OUN.
Despite the favorable conditions along and immediately north of the Red River, I think the weak/absent cap and the fact that storm motion was nearly parallel to the front resulted in a quasi-linear mess. This was made more disheartening when I looked at 0z data and model initializations, and noticed that 850mb was a good 10kts stronger than forecast. Earlier today, I thought the weak 850mb flow would be one of the more important negatives to the event, though this turns out not to have been the case (given the 20-25kts instead of forecast 10-15kts). Several storms clustered up right away and moved nearly parallel to the front. This resulted in convective seeding, which was made worse by the relative lack of a cap. A high-shear, moderate instability set-up put to waste...
