The Diurnal Distribution of Lightning over North Florida and Its Relation to the Prevailing Low-Level Flow

Abstract

Six years (1989?94) of cloud-to-ground lightning data are used to examine the distribution of lightning across the Florida panhandle and adjacent coastal waters and its relationship to the prevailing low-level flow. Only warm season data between 1 May and 31 October are used. The prevailing flow is determined by subdividing the low-level (1000?700 mb) vector mean wind into categories that are either parallel or perpendicular to various parts of the coastline. Moderate wind speeds (2?5 m s?1) generally are found to be more conducive to producing lightning than stronger speeds. Wind speeds stronger than 5 m s?1 likely inhibit the formation of the sea breeze, the main focus for summertime thunderstorms in the region. Onshore, offshore, and parallel flows are found to play important roles in determining the patterns of flash locations in each flow regime. The complexity of the coastline also is found to have a major impact on the flash distributions. The prevailing wind direction is shown to be related to the time of peak afternoon lightning occurrence as well as the frequency of nighttime storms.