A Mesoscale and Storm-Scale Analysis of the Rapid Mini-Supercell Formation and Tornadogenesis Associated With A Remnant Tropical System

Convective storms associated with land-falling tropical cyclones, or the remnant circulations thereof, present a unique challenge to meteorologists charged with warning responsibilities. Such storms are notorious for rapidly developing rotation that falls short of the typical spatial and temporal dimensions associated with mesocylones but still often produce tornadoes. An example of this occurred when the remnants of Tropical Storm Bonnie moved across the County Warning Area of the NOAA/National Weather Service Office in Wilmington, North Carolina on 13 August, 2004. Typical heavy rain and several strong thunderstorms accompanied the passage of the system. Despite the fact that many of the stronger thunderstorms displayed fairly similar rotation signatures on Weather Surveillance Radar-1988 Doppler (WSR-88D) there was only one instance of severe weather. This instance of severe weather turned out to be an F2 tornado that resulted in three fatalities, numerous injuries, and extensive property damage. This presentation will show that the tornadic storm cell developed rapidly along a pre-existing coastal boundary and outflow from a parent storm cell. Although other storm cells strengthened as they crossed the coastal boundary, the tornadic storm cell was assisted by a favorable configuration with the outflow from a precedent storm cell, allowing this particular storm to produce a deadly tornado while all of the other apparently similar storms produced no severe weather.