Lightning Distributions over the Florida Peninsula

Lightning data are a relatively new tool for the study of deep convection. We have examined ten years of data from the National Lightning Detection Network (NLDN) over the Florida peninsula. Data from 1989-98 were organized by map types that indicate location of the sub-tropical ridge (e.g., north of Florida, south of Florida, within Florida). Each day was placed into a map type on the basis of radiosonde-derived wind data from three stations within the study area. Only warm season data between 1 May and 30 September were used. Lightning flash density maps then were generated for each map type.

Results indicate that complexities in the Florida coastline produce four areas of relatively high flash densities. These areas are near Tampa Bay, Ft. Myers, Palm Beach and Cape Canaveral. Our analysis of nocturnal lighting data reveals relations to ocean currents such as the Gulf Stream, as well as coastline orientations.

Results also show that location of the sub-tropical ridge with respect to the Florida peninsula plays an important role in the spatial and temporal distribution of lighting. For example, when large-scale flow is from the southeast, the east coast sea breeze is relatively weak. However, the west coast sea breeze is strong and hugs the coast line, producing lightning that is most intense near Tampa Bay. On the other hand, when the large-scale flow is from the southwest, there is relatively little convection along the west coast, but major lightning activity occurs along the east coast.

This paper will provide insight into the spatial and temporal evolution of convection associated with each synoptic pattern and will identify areas that are favored for convection. Furthermore, the paper will indicate location of convective activity that are not easily understood, thereby stimulating further study.