Diurnal and Spatial Variability of Lightning Activity in Northeastern Colorado and Central Florida during the Summer

Abstract

Lightning location data from northeastern Colorado and central Florida for the summer months of 1983 have been studied to ascertain the diurnal development of spatial distributions of flash frequencies. In both locales, a clearly identifiable influence was found of the underlying topography and resulting diurnal circulations on the time and place of occurrence of lightning ground strikes. Although both locations are strongly convective, lightning exhibited a very large day-to-day variability, since most locations had no lightning on half the days. The study also emphasizes the utility of flash data, once carefully corrected, in studying both the characteristics of lightning and the patterns of topographically induced convection. In Colorado, the total summer flash activity was concentrated just east of the Continental Divide from Longs Peak southward, then eastward along the north side of the much lower Palmer Lake Divide. Two maxima of seven flashes per km2 were located within this peak of activity. First lightning began before noon just east of the Continental Divide, then moved cast during the afternoon; new centers appeared near the Divide again during the afternoon. In the evening thunderstorms moved to the northeast along the north slope of the Palmer Lake Divide. These results verified that lightning activity is in substantial agreement with earlier summer studies of radar and surface winds that define the influence of a low-level circulation in the North Platte River basin. In central Florida, the total summer lightning activity was highest from Cape Canaveral northward along the cast, and westward from the Cape to Orlando. Peak values were over eight flashes per km2. Significant lightning began along this coastal maximum in midafternoon, followed by the thunderstorms in the maximum toward Orlando. Lightning ended over land by 2200 EST, and some activity occurred offshore during the night.