August 16, 2002 - Knox County NE - Supercell



Chase Account by: Jonathan Garner
 
Brian Thalken, Jason Ehmke, and I made it up to Mitchell, SD by 4:30pm. We were anticipating a warm front, which was moving north through Nebraska to make it up into Southeast South Dakota by late afternoon, however, at 5:30pm, we observed several large towers erupt about 50 miles to our south...so it was obvious that we had overshot the warm front just a bit. We made our way south, and by 6:00-6:30, we positioned ourselves to the northwest of a cell displaying decent updraft rotation, but it was having a hard time maturing. We followed this cell east a bit, but then decided to give up on it and head further southeast toward Yankton, SD. As we were heading toward Yankton, a tornado warning was issued for a cell in Knox County, Nebraska (which was moving east/northeast at 25 mph). We knew we were in a great position to intercept this cell if we punched through the core from the north...we decided to do just that, and experienced the classic progression from heavy rain mixed with small hail, to less rain and larger hail (time was 8pm). After we exited the FFD rain core, we immediately observed the vault of this supercell towering above us, and we all feared that our windshield was going to be demolished from hail...however, we got lucky and soon left the hail behind us.

What we observed after the hail was a massive, rotating updraft, with a beaver tail streaming into the base. We drove under the inflow tail and looked off to our west/southwest and observed lots of scud ascending into the base with a hint of rotation. CINH was pretty high in this region, which probably played a role in preventing a tornado from developing, however, the structure on this supercell was amazing. The striated updraft towered high above us, with a flanged, hour-glass shape at the base. 10-minutes later (8:20pm), this storm appeared to have spun itself to death, and practically vanished in thin air. However, there was a second supercell to the northwest of the old one, so we repositioned to the north (8:25pm). This second cell was rotating just as hard, with a smooth laminar base and a flanged appearance in the mid-levels. In addition, it also produced a few funnels just after sunset. All-in-all, today was a great chase...I learned not to give up, even when I'm way out of position.