The NESDIS Operational Convective Precipitation- Estimation Technique

This paper presents the NESDIS operational technique for estimating convective rainfall from GOES data. Estimates and 3-hour outlooks are computed on the Interactive Flash Flood Analyzer (IFFA) and transmitted via the Automation of Field Operations and Services (AFOS) computer systems to Weather Service Forecast Offices, Weather Service Offices, and River Forecast Centers. The technique consists of two steps: (1) locating the active portion of the convective system and (2) computing half-hourly rainfall estimates based on cloud-top temperature and cloud growth or divergence aloft, overshooting tops, mergers, saturated environment (stationary storms), and a moisture correction factor. A warm-top modification is used for cloud tops warmer than −62°C. Three-hour outlooks are based on persistence and extrapolation and trend and expectancy guidelines. Verification results show the average error of the rainfall estimates for a storm total precipitation event is about30%.