Tornado Trailer

The remains of a possible RFD (Rear Flank Downdraft) anti-cyclonic spinup (right) moves (from left to right in this image) along the rear of a supercell that moments before produced an EF3 tornado vortex that heavily damaged the town of Mapleton, Iowa about five miles to the northwest. Some ground debris can still be seen churned up below it. The spinup did not make an audible noise to our chase group. Minutes later our group proceeded northeast along the supercell's SE flank, encountering at least a half dozen more twisters before the night's chase was through. This photo's location was at Sumac Avenue (foreground) and 170th Street (across image) and looks northwest. Time and date was 7:31 PM, Saturday, April 9, 2011.