An Eight-Year Lightning Climatology of the Southeast United States Prepared for the 1996 Summer Olympics

Abstract

The 1996 Summer Olympics will be held in the Atlanta, Georgia, vicinity and several other sites in the southeast United States between 19 July and 4 August 1996. This period coincides with the peak thunderstorm season, so the threat of lightning casualties cannot be taken lightly since Georgia and surrounding states with Olympic venues rank quite high in the United States in annual lightning casualties and the casualty rate per population. Flash density and thunderstorm day estimates for July and August show that the greatest cloud-to-ground (CG) lightning activity (> 5 flashes per square kilometer) occurs near the seacoasts and over the Florida peninsula. Cloud-to-ground flash activity decreases as distances increase from the coastlines, reaching a minimum (< 1 flash per square kilometer) along the North Carolina–Tennessee border. However, there are also important maxima (> 3 flashes per square kilometer) in and around Atlanta. The frequency of CG lightning reaches a maximum in the late afternoon and early evening hours in the Atlanta area. Lightning reaches a maximum in the midafternoon at Wassau Sound near Savannah Beach. As expected, the lowest chances of lightning are from midnight to noon, while probabilities are slightly greater during these hours along the coasts. Flash densities for July and August may vary as much as 2–3 flashes per square kilometer from year to year in most locations. When lightning begins, the chances are greater than 1 in 3 that lightning will still be occurring 1 h later at most venue sites; the chances are 1 in 5 that lightning will be present after 2 h.