Between January 2011 and August 2011, three of the top five worst tornado outbreaks in U.S. history occurred. Some may make the hypothesis that this is due to climate change. To test this theory, the climate normals of possible severe thunderstorm days in the Cincinnati Metropolitan area were examined. This area was chosen due to its high population and its location near the jet stream and Tornado Alley. To do this study, three stability indices were chosen from all 0Z soundings during the last 30 years. The stability indices were the Lifted Index, K-Index and the Convective Available Potential Energy. Before the detection of trends got underway, the decadal and 30 year climate normals for the monthly seasonal and annual stability indices were first derived. Afterword, an examination of the climate normals revealed some trends. The results showed the month of July had the highest number of possible severe weather days, while the winter months mostly had none. Between the months of May and September all indices were trending towards more unstable atmospheric conditions. The decadal climate normals for the seasonal: spring, summer, and fall stability indices for the decade of 2001-2010 were always higher than their 30 year climate normals. This suggests climate change has an effect on the frequency of possible severe thunderstorm days, but more study is needed.

Decadal and 30 Year Averages for Seasonal CAPE Stability Time Period Winter Spring Summer Fall Vary to Extremely Unstable 1981-1990 0.000 1.795 12.083 1.156 1991-2000 0.000 0.845 16.771 1.042 2001-2010 0.000 2.4315 23.362 0.865 1981-2010 0.000 1.779 18.029 1.003 Moderately Unstable 1981-1990 0.000 3.168 21.826 5.418 1991-2000 0.000 5.098 24.360 4.078 2001-2010 0.000 6.974 27.5978 5.924 1981-2010 0.000 5.306 24.8 5.222