Hurricane Irma: Assessing the Local Tornado Threat and Corresponding Potential Impacts across East Central Florida

Hurricane Irma made landfall along the Lower Florida Keys on September 10, 2017 as an intense Category 4 storm. After a secondary landfall along the lower Southwest Florida coast, it continued to move northward around 10-12 mph over inland areas along the western side of the peninsula. Irma’s track and large wind field offered a favorable tornado environment for East Central Florida, especially relative to local kinematics. A productive breeding ground was found over the warm and moist coastal waters for spawning an outbreak of mesocyclones which quickly moved toward the coast. Many of these produced tornadoes which added to the destructive nature of the overall wind event over land. As many as ten tornadoes have been confirmed having identifiable damage paths. However, the actual tornado count is assumed to be under-reported with several occurrences likely lost to Irma’s larger scale wind impacts, especially within rural areas. Even so, considerable tornado impacts were realized particularly for locations in proximity of the coast with only one occurrence confirmed well-inland. This paper will examine the buoyancy and shear evolution of the tornado environment, the changing threat across small time and space scales, and subsequent implications on the tornado warning strategy. An inspection of individual tornadoes will be highlighted. Certain strong mesocyclones which were not tornado producers will also be considered.