Climatology of heavy rain events in the United States from hourly precipitation observations

Flash flooding is frequently associated with heavy precipitation (defined h ere as greater than or equal to 1 in. h(-l)) occurring over a short period of time. To begin a study of flash hood-producing rain events, the Hourly P recipitation Dataset (HPD) is used to develop a climatology of heavy rains on timescales of 3 h or less across the contiguous United States. Analyses of this dataset show a distinct seasonal cycle in the distribution of heavy rain events that begins along the Gulf Coast and expands into the midweste rn states during the summer. This general evolution is very similar to that observed for hash floods, suggesting that the HPD can help in defining the climatological threat for flash floods.