This study deals with the microphysical and electrical evolution of a thunderstorm that occurred on August 9, 1991, during the Convection and Precipitation/Electrification (CaPE) Experiment in eastern Florida. During its approximately 1-hour lifetime, the storm was penetrated several times by the Institute of Atmospheric Sciences' T-28 aircraft at midlevels. It was also penetrated at low and middle-levels by a National Oceanographic and Atmospheric Administration (NOAA) P-3 and scanned by three radars, one of which had multiparameter capabilities, operated by the National Center for Atmospheric Research. Two stages of the storm's evolution are analyzed herein during which the storm grew to produce precipitation and lightning. The first stage, sampled during the first T-28 penetration at 5.25 km (-3 ¿C) and the P-3 at 6.4 km (-10 ¿C), was characterized by a 2- to 3-km wide updraft (maximum 14 m s-1) with cloud liquid water contents up to 4 g m-3, low concentrations of graupel at -10 ¿C, and small to medium raindrops in concentrations of less than 200 m-3 at -3 ¿C. A downdraft region also existed that was devoid of cloud liquid water, but contained graupel up to 2 mm. Radar data (ZDR) are consistent with a coalescence-dominated precipitation generation mechanism followed by transport of drops in the updraft to heights with temperatures colder than -7 ¿C, where freezing formed graupel that continued to grow by riming. Electrification during this stage remained weak. The second stage, sampled during the second and third T-28 penetrations and the second P-3 penetration, was characterized at midlevels by a narrower updraft and a more diffuse, broad downdraft separated by a 1- to 2-km wide transition zone. The updraft continued to show significant cloud liquid water (~2 g m-3) with few precipitation particles, while the downdraft had very little cloud liquid with graupel in concentrations >1 l-1. The transition zone shared both updraft and downdraft characteristics. The increase in ice concentration was accompanied by a rapid increase in the electrification of the cloud with peak electric fields reaching -20 kV m-1 at T-28 altitude and the detection of lightning by ground-based sensors and pilot report. As time progressed, precipitation particle concentrations reached several per liter at midlevels in both updrafts and downdrafts. The observations are consistent with electrification through a precipitation-based mechanism involving the development of the ice phase. ¿ American Geophysical Union 1996