RE: April 13 Eastern IA storms
I have a collection of data (SFC, UA, profiler, radar, satellite, soundings, etc) from that day. PM me and I'll zip it and send it. BTW, I live in Iowa City. The Iowa City tornado path started about 1/4 mile from my house. I watched the nighttime tornado as it tore through the city, as well as an earlier tornado west of Cedar Rapids.
This is a very interesting day to do a case study of. Basically, the synoptic setup had a WF well to the north, along the IA/MN border. A look at morning data suggested that that area would be the chase target for afternoon storms. Morning dew points were very low throughout IA - in the 40's in all but the southwest part of the state. As the day progressed, a narrow wedge of rich SFC moisture surged northeast, reaching central IA by mid-afternoon. Meanwhile, a compact mid-level disturbance lifted to the NE out of KS - examine the profiler data. Models based on 12Z data underestimated the strength of this feature. Storms fired in central IA by late afternoon, and moved E towards eastern IA. SFC flow became increasingly backed in response to the shortwave. The moisture arrived in Eastern IA just an hour or two prior to the arrival of the storms, and LCL’s dropped rapidly after 00Z (00Z DVN sounding – only 60 miles to the east – still indicated poor LLVL moisture and an LCL of nearly 2000m AGL)! And that was only 90 minutes before the tornado hit IC.
[FONT="]- bill[/FONT]
