Centennial Honors College Western Illinois University Undergraduate Research Day 2014 Poster Presentation Differences in Surface and Atmospheric Conditions between Spring and Fall Tornadoes in the State of Illinois Alexander Leslie Facutly Mentor: Jongnam Choi Meteorology Tornadoes in spring month are common in Illinois, while tornado in fall is quite rare. This study analyzes surface and atmospheric conditions of a tornado occurred at Washington, IL on November 17, 2013 and a tornado in the town Streator at LaSalle County on June 5, 2010. This study examines the difference in atmospheric environments for both tornadoes. For better understanding surface and upper-air conditions of both tornado outbreaks, this study used variables from the surface to the tropopause, including vertical structure, geopotential height, and thermal and moisture advection at standard pressure levels at prior or subsequent hours of these tornadoes. Reanalysis gridded data from the online NCEP/NCAR data archive was used to reconstruct synoptic scale atmospheric patterns at pressure and surface levels Unidata’s Integrated Data Viewer (IDV) was used to analyze and create composite data and maps. The preliminary results show that both tornadoes have very similar thermal and moisture advections to tornadoes. However, maps show difference in vorticity advections at 500 hPa and divergence at 300 hPa for both tornadoes at both tornadoes. Findings from this study enable meteorologists to make a better prediction on outbreaks of tornadoes at the central Illinois which potentially induce numerous casualties by the storms.