Higher Terrain Impacts of Eastern Middle Tennessee on Tornadogenesis

Meteorologists at the National Weather Service office in Nashville, Tennessee have noted that, during recent severe weather events, numerous supercells in otherwise favorable environments to produce tornadoes did not become tornadic until they reached the higher terrain in eastern Middle Tennessee. This region, known as the Cumberland Plateau, consists of hilly, rugged terrain reaching upwards of 2500 feet MSL. Supercells that move eastward across Middle Tennessee into the Cumberland Plateau travel over terrain that rises as much as 2000 feet in elevation in a relatively short distance.

This presentation will discuss the likelihood of supercell thunderstorms becoming tornadic as they progress into eastern Middle Tennessee. The assumption is the higher elevations of that region effectively lower the height of the lifted condensation levels (LCLs) above ground level. Prior research has shown that lower LCL heights can be a major component in tornadogenesis, and previous studies of the effects of higher terrain on LCL heights and impacts on supercells and tornadoes will be reviewed. Data from severe weather events in 2011 and 2012 across Middle Tennessee will be examined to determine if there is a correlation between the higher topography of the Cumberland Plateau, LCL heights, and an increased likelihood for tornadic supercells. Results from this study and the impacts on improving forecasts, warning operations, and decision support services will be discussed.