Chase Log: April 28th, 2006
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: 500 miles
Target Area: Childress to Guthrie (TX)
Chase Area: Childress, TX, to Olustee, OK
Maximum SPC Risk category: Moderate
Watches:
Tornado Watches 256, 257, 258, 259, 260
Mesoscale Discussions (MCDs): 667, 668, 669, 670, 671, 672, 673, 674, 675, 676,
I went out with Robin, Dan, and JR, targeting an area near and south of CDS. We arrived in CDS and hoped that the convection that fired around 1pm west of ABI and south of Quanah wouldn't become a problem. By mid-late afternoon, new convection was developing along the cold front - dryline intersection to the west of CDS. We followed this intersection southward for a bit, but it was becoming quite obvious that the cold front was undercutting the convection. It's never a good thing when you have a southward moving cold front with storms that are moving NE slowly... So would develop sw of CDS, but then quickly get undercut... We did see several dust devil / gustnado vortices right along this cold front, which was kind of neat. Between CDS and Matador, we decided to head back north to see if we could catch up with the cell that was entering Harmon Co OK. We moved through Hollis, and stopped in Duke after seeing that this sw OK storm was weakening. New storms had developed back to the SW near Matador, but we were fearing that they would see the same fate as a handful of other hopefulls saw earlier in the day... We made it to Quanah, but the cells were lining out, so we opted to call it a day.
I think there were several failure modes with the convection in the northern part of the risk area... First off, the convection that fired around noon in western north TX moved eastward only very slowly, so that by mid-afternoon, there was only a 2 county wide area between the dryline and the cool outflow from those storms. In addition, this cooler air was advected towards the CDS area on the southeasterly sfc flow. Secondly, the cold front continued to move southward faster than I was anticipating, so the half dozen or more storms that did try to develop at the cold front / dryline intersection were quickly undercut and left in cooler, more stable air. Third, the storms seemed to initiate in a SW-NE fashion. We a northeasterly shear vector and southwesterly flow aloft, there was a tendency for upscale growth to line segments (anvil seeding, etc). Related to these previous two points is the flow in the mid-levels, with a slight backing vertical wind profile in the ~700mb area per local VWPs and RUC analyses immediately ahead of the dryline.
I can say that the hodograph on the Friday evening (00z) FWD sounding is one of the most impressive I have seen in a long time. >500 0-1km SRH and 75kt 0-6km shear? That 0-3km layer on the hodograph is incredible! The low-level hodograph on the DRT and OUN soundings were nearly as impressive... Man, I would have liked to have seen what would have happened if we had more significant destabilization Friday given the shear that was in place...
04-28-2006 Chase Pictures
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