EF0 tornado in Posey County, Indiana

An EF-1 (peak of EF-0 for the Posey County portion) tornado that began in far northeast Gallatin County, IL crossed into extreme southwest Posey County, IN during the early morning hours of Tuesday, April 2nd, just south of the confluence of the Little Wabash and Wabash Rivers. The tornado lifted shortly after crossing into Posey County, producing tree damage visible from the Illinois side of the river. Estimated peak winds on the Posey County side of the track were 80 mph.

Early morning, the surface low was located just north of St. Louis, Missouri, lifting to the NNE as it rapidly deepened. For Southwest Indiana, early morning effective bulk shear was 65-70 kts, with a very high 25-30 kts of 0-1 km shear, while SRHs were around 150-200 m2/s2. MLCAPE was 1000 J/kg, and mid-level lapse rates were 7 C/km. A 70-90 kt mid-level jet was west of the Quad State. A strong capping inversion suppressed storm activity in the evening, but the strong lift and upper level diffluence won out early morning. Two lines of storms developed after midnight in Southeast Missouri. The first just missed to the north of Gibson County. The latter was a very potent thunderstorm line racing eastward early morning April 2nd. This line continued throughout the day all the way to West Virginia, being designated a derecho. For Southwest Indiana, widespread wind damage occurred with this line, and sections of the line that took a north-south orientation had a much more favorable line-normal component of shear promoting QLCS tornado development. This was the case for Posey, Vanderburgh, and Warrick Counties. Seven tornadoes originated in Southwest Indiana: 2 (both EF-2) in Posey County, 3 in Vanderburgh County (1 EF-2 and 2 EF-1), and 2 in Warrick County (both EF-1). Including county crossovers, there were 4 tornadoes in Posey County, 4 in Vanderburgh County, and 6 in Warrick County. Four tornadoes crossed from Vanderburgh into Warrick County at approximately the same time. There were also 3 microbursts/macrobursts south of the tornado tracks: a microburst in Posey County, a macroburst that progressed from Parkers Settlement in Posey County to Melody Hill in Vanderburgh County, and a microburst south of Boonville in Warrick County. A total of 19 tornadoes were found during this event, the highest single day total for the NWS Paducah forecast area since Halloween 2003 (also 19). Vanderburgh County EMA tallied up at least 42 structures damaged (including 5 with roof damage, 7 houses damaged or destroyed, 7 hours with trees on them, 15 barns or storage structures damaged or destroyed, a gas station overhang blown over, and a radio tower blown over). Additionally, 4 semis or semi-trailers and 4 cars were blown over. Numerous metal power poles were blown over and bent in half along US-41.