Composite Analysis of Cool-Season Florida Tornado Outbreaks

Abstract

This study presents a multiscale environmental analysis of 33 Florida tornado (1979–2016) and 29 null events (2003–2019). A tornado event was defined as ≥ 4 tornadoes within a 24-h period during December–May, which was chosen to eliminate events associated with tropical cyclones. Null events were defined as periods when the NOAA Storm Prediction Center had tornado outlook probabilities ≥ 5% over any part of Florida, but < 4 tornadoes occurred in 24 h. Central Florida experienced the largest number of tornado events, while most null events occurred in the Florida Panhandle. Tornado events occurred slightly more frequently during El Niño and negative Arctic Oscillation, in contrast to cool-season events elsewhere in the United States. Using the North American Regional Reanalysis, a composite synoptic analysis showed that compared to null events, tornado events were associated with a coupled divergent jet streak region, a more amplified anomalous mid-tropospheric trough, a surface cyclone located farther south (Gulf of Mexico vs. Tennessee Valley), and larger equivalent potential temperature anomalies. While both event sets featured high-shear, low-CAPE environments that are typical of southeast United States tornado events, tornado events exhibited larger storm-relative helicity and 0–6-km vertical wind shear. Overall, results suggest that synoptic pattern recognition techniques and mesoscale parameter spaces can help forecasters in identifying potential Florida tornado events.