On 18 August 2011 at 0307 UTC (11:07 PM EDT) the TRMM satellite traveled above an area of organized shower activity in the Caribbean Sea that the National Hurricane Center (NHC) forecasts will soon become a tropical cyclone. TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) data show that this tropical wave south of Jamaica contained several areas of convective thunderstorms that were dropping rainfall at the rate of over 40 mm/hr (~1.6 inches).

TRMM's PR data show that some thunderstorm towers in this stormy area were higher than 13 km (~8 miles).