Wednesday, April 14, 1999

Chase Accounts

Tim Vasquez & Shannon Key -- With a cold-core low crossing southern Oklahoma and clear skies and 60-ish dewpoints here in Norman, it looked like we'd get a round of Cb's springing up in relatively clear skies -- a great photo opportunity! Shannon Key and myself headed north out of Oklahoma City at 2000Z. We drove straight north to escape a broad cirrus shield threatening to kill solar heating, hoping that the area along the fringes, near Stillwater, would "light up".
          As we passed Guthrie around 2030Z, we saw that a N-S line of hard towers was forming to our west. As we were expecting an E-W orientation, aligned with the clear slot, this suggested that the cold front was at the heels of this cumulonimbus line. Near Mulhall, and with nothing forming in the clear slot (now filling with cumulus), we decided to head toward the main tower in this line, which was now darkening the western sky quite ominously.
          By 2100Z near OK51/OK74 the storm was in plain view -- the features were somewhat linear but a rounded updraft base began coming together to our SW and inflow was quite healthy, with winds out of 100/15 kt. We dropped south to Crescent, and at 2116Z the base started rotating rapidly. I stopped and got a tripoded shot of this circulation, about 3 miles to our WSW. Wow!! This lasted only about one minute, and the cell then gusted out and sent us scrambling southeastward, closely followed by a rain/hail-filled core. We parked east of Guthrie, but by this time it was looking very outflowish. We tailed the linear updraft east to Langston and Perkins, watching it transition into a messy squall line structure.
          The "vaulted" updraft was remarkably detached from the precipitation area, forming incredible "sideways"-oriented bubbles on the sides of the vault. I stopped near a house south of Perkins and grabbed my still-camera bag out of the trunk -- two dogs immediately bounded off the porch running for me, and I jumped back in the car and had to blow the horn to get the dogs away from the car. I was able to move just in time to get some photos of this vault before the weak rain core caught up. We left the storm there, heading back to Norman under beautiful, scud-filled skies (with VERY low bases) that alternated with sunshine.
          After we got back I looked at some radar archives and saw that the Crescent cell had an interestingly "kidney-bean" shape at 2130Z. Was anyone else on this storm? What did you see? Did anyone look at any velocity products? Given that we were just out for some photogenic Cb's, this was a *lot* more than we had hoped for!

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Radar data provided courtesy of Weathertap, Inc.