The Role of Surface Divergence and Vorticity in the Life Cycle of Convective Rainfall. Part II: Descriptive Model

Abstract

Three stages, prerain, mature and decay, in the life cycle of a convective storm are shown by compiling surface observations from 12 well-organized Florida summertime thunderstorms. In the mature stage, a distinction is made between stationary and moving storms. The prerain phase is characterized by cyclonic inflow, the mature phase shows cyclonic inflow and anticyclonic outflow simultaneously, while in the dissipating stage only anticyclonic outflow exists. Numerical values for the updraft and downdraft areas, upward flux of water vapor, maximum divergence and vorticity, and rainfall are presented. Moving storms last longer (by 25 min), transport roughly four times the moisture of a stationary storm and produce more rain over a larger area. These numbers provide valuable information not previously available for the surface layers of the convective storm environments.