Characteristics and storm evolution associated with the 30 May 2003 tornadic event over central Illinois

On 30 May 2003, a tornado outbreak occurred during the late afternoon and early evening across Central Illinois. Seven confirmed tornadoes occurred during this period with one tornado (Logan County Illinois tornado) produced F2 damage over parts of Logan and De Witt counties in Central Illinois. This tornado caused major structural damage over the southern parts of Clinton Illinois where numerous businesses were damaged or destroyed. The Logan County tornado was spawned by a supercell located near the upshear flank of a larger area of strong to severe convection. The larger cluster of storms was classified as a "Leading Stratiform' (LS) convective system. The Mesoscale Convective System (MCS) gradually evolved into a bow echo complex over West-Central Indiana. Since this severe weather episode occurred during the Bow Echo and MCV Experiment (BAMEX), special rawinsonde observations were taken at 2100 UTC (30 May 2003) and 0000 UTC (31 May 2003) from National Weather Service (NWS) sites at Davenport Iowa (DVN) and Lincoln Illinois (ILX) respectively. Additionally NOAA P3 and the NRL P3 aircraft recorded airborne Doppler radar observations along the northern and southern flanks of the tornadic supercell while a high-altitude jet released a number of dropsondes over the larger convective system.

This presentation will specifically focus on the upshear flank tornadic supercell which caused substantial damage over parts of Logan and De Witt counties including the community of Clinton Illinois. Sounding analysis from DVN, ILX and dropsondes from the high altitude jet will show the thermodynamic and vertical wind shear structures preceding and during the period of severe convection. Doppler observations from WFO ILX will also be presented to reveal the evolution of the tornadic mesovortex. Specifically, we will present the characteristics of the mesovortex leading up to the time of the first and second tornado occurrence.