Chase Log: May 04th, 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.
Total Distance: 550 miles
Target Area: Near Kinsley, KS
Chase Area: Around Woodward, OK
Maximum SPC Risk category: Moderate
Watches:
Mesoscale Discussions (MCDs):
Potential for a good tornadic supercell day as moderate southwesterly flow aloft above a moistening boundary layer was forecast to yield an environment favorable for supercells and tornadoes. A dryline bulge had been forecast across southwestern KS by the NAM for several runs prior to the day, and it looked as though there would be an enhanced potential for strong tornadoes immediately ahead of the dryline bulge near DDC. Strong shear + strong CAPE (>3000 j/kg) + low LCLs + discrete mode = potential for a good chase day.
By the time we made it to Woodward, it was apparent that low-level moisture was mixing out a bit across northwestern OK and southwestern KS. For the afternoon, Tds were largely in the 57-61F range immediately ahead of the dryline in this area, but the >68F dewpoints persisted only ~60 miles east of the dryline. As we crossed through Sitka, we were somewhat discouraged by the lack of any appreciable boundary layer cumulus. Alas, we continued northward in hopes that the dryline bulge would material and provide enhanced surface convergence. Bucklin was our next stop, at which time we received word that the X-band Dual-pol radar that Howie Bluestein, Robin Tanamachi, and Kerry were riding in had blown a tire about 10 miles south. We headed back south to meet of with them as they waited for AAA to dispatch assistance. Around that time, a couple of strong storms rapidly developed near Canadian, TX, and quickly took on supercell characteristics. With the blessing of the X-pol riders, we blasted southward to meet up with the supercell southwest of Woodward. Although a tornado produced by that supercell had lifted by the time we reached it, we waited for it to produce again. Alas, it never really looked like it was close to tornadogenesis again, with a relatively high, laminar-looking cloud base. To make matters worse, cloud-base motions weren't even particularly impressive. As the cell started to slowly diminish in size, it was obvious that it was slowly dying.
As the sun set, we noticed another very strong storm to our NNW, crossing the OK-KS border south of Sitka. With a NNE to NE storm motion, and darkness setting in, we didn't think we'd have a chance to catch up with it until well after dark. So, we decided to call of the chase at that time. Shortly after we made that decision, the supercell near Sitka organized further. At one time, there were three circulations apparent to the northwest through west of Protection, KS, very reminiscent of the event in the same area a couple of weeks prior. As it passed north of Protection, however, an extremely strong low-level mesocyclone developed. The tornado produced by this low-level mesocyclone would go on to become the first EF-5 tornado after causing catastrophic damage in the town of Greensburg. As that tornado occluded to moved NNW, another extremely intense, and extremely large, circulation developed to the ENE of Greensburg. This tornado certainly looked every bit as strong and large of the Greensburg tornado per DDC radar data. In fact, this second extremely large tornado may have even been stronger than the EF5 tornado that destroyed much of Greensburg. I could go on and on about this supercell, a storm that is the most impressive and intense I have ever seen on radar. Absolutely amazing, with a myriad of extremely interesting storm-scale processes apparent.
I've uploaded some radar imagery of the Greensburg supercell HERE. Interestingly, we were only about 15-20 miles from Greensburg during the mid-afternoon when we stopped in Bucklin. In addition, the Xpol truck blew a tire only about 10 miles from the path of the Greensburg tornado. On a somewhat unrelated note, while en route to Fort Apache for a mission project before 11th grade with my church, we actually stopped in Greensburg. Wierd.
05-04-2007 Chase Pictures
Click on any photo to see a larger version
