This talk will report on the preliminary results of a comprehensive study of cool season tornadoes in the southeast United States. Previous research has shown that there is a relatively high frequency of tornadoes in the overnight to early-morning hours during the cool season in the Southeast, particularly in areas close to the Gulf of Mexico. In fact, most strong tornadoes (F2 or greater) in Florida occur during the cool season, associated with extratropical cyclones. The cause of this nighttime maximum during the winter months is not well understood, and one focus of this research will be on gaining a better understanding of the causes of this phenomenon.

Previous research has also documented the importance of return flow of warm, moist tropical air to the Gulf region after the passage of cold fronts through the Gulf in the development of potential severe weather scenarios along the Gulf coast. The warm Loop Current in the Gulf also can increase fluxes of heat and moisture into this return flow air, which can lead to rapid air mass destabilization. It has also been shown, however, that forecasting the trajectories of return flow air is difficult, and that numerical models are not able to accurately forecast the modification of the boundary layer (partially due to lack of data over the Gulf), which can be important in determining the severe weather potential over the Southeast.

The focus of this talk will be on the preliminary results of the initial phase of the research for this project, which will seek to establish the detailed climatology of severe weather in the southeast United States. Mean dynamic and thermodynamic conditions associated with strong tornadoes and/or tornado outbreaks in the Southeast will be computed using proximity soundings and NCEP/NCAR reanalysis data. In addition, two preliminary case studies will be completed in order to compare conditions associated with a tornado outbreak over central Florida (22-23 February 1998) to those during a similar-looking null event, where tornadoes were forecast, but only one F0 occurred on the Florida peninsula (14 March 1999).