3-DIMENSIONAL KINEMATIC AND MICROPHYSICAL EVOLUTION OF FLORIDA CUMULONIMBUS .1. SPATIAL-DISTRIBUTION OF UPDRAFTS, DOWNDRAFTS, AND PRECIPITATION

This paper is the first in a three-part study that examines the kinema tic and microphysical evolution of Florida cumulonimbus and focuses on the convective-to-stratiform transition of the storm. This first pape r lays the groundwork for the subsequent papers by defining the proble m under study, delineating the setting for the storm, and describing t he spatial distribution of updrafts, downdrafts, and precipitation. Hi gh-resolution radar data of a typical line of storms associated with t he Florida sea breeze is the centerpiece of this study. The high-resol ution data reveal details of the internal structure of the squall line that were beyond the resolution of previous squall-line studies. Rada r reflectivity filled in between cells at upper levels as the storm ev olved. Reflectivity values were only weakly associated with updraft an d downdraft magnitude. The updrafts and downdrafts in the storm tended to be irregular in their three-dimensional shape and less than 5 km i n horizontal extent. At any given time, updrafts and downdrafts al a v ariety of strengths were present at all levels throughout the storm. T he stronger drafts were usually closer to the leading edge of the stor m. Upper level downdrafts were often located alongside upper-level upd rafts. Updrafts tended to drift upward from lower levels and weaken as they aged.