Chase Log: February 23rd, 2007

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.

MAP

Total Distance: 430 miles
Target Area: Childress, TX
Chase Area: Near Memphis / Wellington, TX
Maximum SPC Risk category: Moderate
Watches: Tornado Watches 27, 28, and 29
Mesoscale Discussions (MCDs): 177-181, 183, 185, 186, and 188

A powerhouse upper-level low/trough was forecast to dig/amplify and move out of the Rockies during the late afternoon, evening, and overnight hours of Feb. 23rd. The two largest unknowns were moisture availability and timing of initiation. It wasn't surprising that the former was a known issue, since climatology argues strongly against a significant tornadic supercell event in western Oklahoma and the eastern Texas panhandle in late February. Regardless, the mid-upper 50s dewpoint forecasts were expected to lead to ~1000 j/kg CAPE in a slender corridor east of a dryline. With very strong flow at all levels, shear profiles were extremely supportive of tornadic supercells (50-60kt 0-6km shear, >400-500 m2/s2 0-3km SRH, etc). Despite this, there were many questions regarding the timing of initiation. With the main low/wave forecast to move into the Plains overnight, confidence was not high in daytime initiation (aided by the fact that sunset is ~6:30pm -- quite early).

I (along with my wife, Dan Dawson, and Jana Houser) targeted CDS, and made it through Hollis as convection was firing to our west. We stopped and waited in Wellington, hoping that the mess of convection to the west would settle down (i.e. a couple of supercells would come out of that intact). Around 5:45 (I think....) we noticed a left-split starting to move northeastward from the southern storm (Quail TX storm). Thinking that it would impact the cell near I40, we opted to drop west-southwestward toward Memphis and Quail. Rather hilly terrain and questionable roads made it difficult to get a view of the storm base until we got into better position around 6:15pm. By this time, the mesocyclone was beginning to weaken, though we observed pretty nice RFD action. From our view (on FM1547 ~3mi S of Quail), the storm looked to be on the wet side of classic (or even HP), with the primary meso tucked well into the precipitation. I wasn't able to look at radar much since I was driving, but that's what it looked like to me. The more I think about it, there may have been some flanking-line convection that developed and moved into the main body of the storm. I suppose I'll figure it out when I review radar imagery tomorrow.

I'm interested to see pics/video or read accounts of the tornado reported near Quail. I think the 0022UTC report came when we were forced to turn around on a terrible, sand-dirt road about 1 mi S of Quail. We spent 5-10 minutes driving around trying to find a hill on which to park, and our one attempt to get closer was reversed owing to fear of getting stuck in sand / loose dirt on a road that had a tall hill on the storm-viewing side. UGh.