Climatology of severe thunderstorm atmospheric conditions

The effects on Climate change on the probability, severity, and spacial distribution of severe thunderstorm conditions and heavy rain events are a topic of current discussion. As a first step toward understanding the significance of these effects, a climatology of severe thunderstorm atmospheric conditions has been developed. This climatology was developed from radiosonde observations throughout the eastern two-thirds of the United States. Four quantities, including Convective Available Potential Energy (CAPE), Convective Inhibition (CIN), K-Index (KI), and Lifted Index (LI), were computed from 00 UTC soundings, corresponding to the most convectively active time of the day, for the months of March through November from 1983 to 2012. All data were evaluated based on quality and completeness. The 30-year monthly and seasonal averages were found for six regions east of 107 degrees west longitude. Results show the percentage of days when atmospheric conditions are moderately or very unstable according to KI or LI is greatest in the southern Great Plains during the spring and along the Southeast Coast during summer and fall. Based on CAPE and CIN, which were only analyzed for the summer season, The Southeast Coast has the highest frequency of summer days with moderately to very unstable conditions and is the region least affected by days of high CIN. These results agree qualitatively with the seasonal and geographical distribution of severe weather and heavy rain events, giving credence to the use of atmospheric thermodynamic quantities as a basis for calculating the climatology of atmospheric conditions.