Buoyancy by Season: A Climatology of Tornadoes and Surface-Based Convective Available Potential Energy in the Memphis, Tennessee, CWA

Buoyancy parameters such as surface-based convective available potential energy (SBCAPE), play a key role in forecasting tornado potential and intensity. Seasonal differences in SBCAPE values relative to tornado threats is understood at a basic level, such that the warm and cold seasons are characterized by relatively large and small SBCAPE values, respectively. However, the need for more accurate forecasting requires a detailed understanding of the inter-seasonal trends of the buoyancy/tornado relationship. This project explores the correlations of buoyancy by season to tornado frequency and EF Rating through a climatology of all tornado events and respective SBCAPE values from 2008-2018 within the NWS Memphis WFO CWA. Tornado reports are found using Mississippi State’s Tornado Database. SBCAPE data is retrieved through NOAA’s National Centers for Environmental Information (NCEI) 12km NAM and 13km RAP/RUC analyses data archive and analyzed through UCAR’s Integrated Data Viewer (IDV). SBCAPE values, tornado intensities, and frequencies of events are presented through several “filters” by season such as diurnal and storm mode. Preliminary results show that warm seasons are characterized by higher SBCAPE values, weaker EF ratings, and smaller frequency of tornado events. Contrary to the initial hypothesis, the cold season exhibits similar SBCAPE values to that of Spring, higher EF-Ratings, and a moderate frequency of cases. These findings suggest that the buoyancy/tornado relationship is not straightforward, and that cold season tornado potential can be just as volatile as the typical Spring events in this CWA.