May 8, 2004 - Central Iowa


  
Chase Account by: Jonathan Garner
  
Today's target was around the Atlantic, IA region. Since Brian and I departed for our chase today at 4:30pm, we were able to monitor initiation via internet as we drove north to Omaha and then east along I-80 toward central IA. One cell, which briefly looked supercellular developed just west of Des Moines and then weakened as it moved northeast. However, a second cell developed near Atlantic at around 5:30pm along a stationary frontal boundary. This cell rapidly strengthened, and by 6pm, we were in position to intercept. By 6:30-7pm, we were just south of the updraft, and the storm appeared to be pushing outflow hard from the north. Then, the NWS issued a tornado warning for an area of the storm that was just to our northeast. We raced east along highway 44 and observed alot of dust being kicked up underneath the base. As we went further east, we eventually spotted a developing wall cloud to our north, with lots of scud getting sucked into this feature horizontally. Rotation within this wall cloud began to increase, and the base of the cloud began to lower. It appeared it was ready to produce a tornado, but the mid-level mesocyclone appeared to wrap rain around from the southeast, which then obscured our view. We continued east, observing CG's in every direction. The structure this storm was beginning to take on rapidly improved as well...it appeared to be evolving into a classic, text-book perfect HP supercell, with a large, rounded updraft which rotated back around to the northeast flank, and surrounded a large, circular rain core on the rear flank. The back lighting was terrific for photography, and we followed the storm east all the way to Des Moines. The storm had a continuous tornado warning issued for it from ~6:30 to 8:30pm. We called it a day at sunset, with a great lightning display present to our north to keep us entertained all the way back to Nebraska.