The Next Generation Weather Radar (NEXRAD) is slated to play an important role in the integrated and automated air traffic control system being currently planned by the Federal Aviation Administration One major point of debate is the minimum rate at which weather data collected by NEXRAD must be updated so that no phenomena potentially hazardous to aviation go undetected This paper presents the methodology and results of a study to estimate the lifetimes of significant features in typical storm phenomena for situations other than takeoff or landing These results are of direct relevance in deciding NEXRAD system data update rates. Two methods are used for the lifetime study: photo interpretive and computer based correlation Several storms are studied using both methods It is found that the storms studied contain no feature that might have been missed by a 5-min scan cycle provided that concurrent reflectivity, radial velocity, and Doppler spectrum width data at several elevations are utilized in the detection of hazardous phenomena.