Characteristics of East-Central Florida Tornado Environments

Abstract

Climatological analyses indicate that strong morning tornadoes in the dry season, and weak afternoon tornadoes in the wet season, are significant forecast problems in east-central Florida. To address this issue, an analysis of upper-air soundings for Tampa Bay, West Palm Beach, and Cape Canaveral, Florida, released within ±2 hours of tornado touchdowns in the County Warning Area (CWA) of future National Weather Service (NWS) Weather Forecast Office (WFO), Melbourne, Florida, was completed. Mean dry- and wet-season tornado-proximity soundings to 200 mb were produced, and selected mean diagnostic parameters and variance statistics computed. Both dry- and wet-season tornado environments were associated with deep moist layers overlain by dry air, but no capping inversions. Dry-season cases were characterized by lower-tropospheric ow values well above normal, very low Convective Available Potential Energy (CAPE) and Bulk Richardson Number (BRN), strong speed and directional shear at low levels, a strong midlevel dry intrusion, and a maximum wind at 200 mb. The thermodynamic environment of the wet-season cases under westerly flow was close to mean seasonal values, but U increased steadily above 650 mb to a mean westerly maximum wind at 275 mb. These middle and upper-level winds, greatly exceeding mean seasonal values, allow thunderstorms developing along low-level convergent boundaries to be organized and sustained by the production of strong, persistent, tilted updrafts and continued low-level inflow of high ow air.