Synoptic and Meso-Alpha Scale Meteorology of Wyoming Flash Floods

摘要

The combination of high terrain features, warm temperatures and moisture intrusions makes Wyoming susceptible to dangerous thunderstorms which produce very heavy rains with flash floods. Since such storms are difficult to forecast, a study was performed investigating synoptic and meso-alpha scale meteorological factors associated with their occurrence. Data and meteorological patterns were examined for an eight-year period for all days in which Wyoming experienced at least one flash flood. Climatologically, it was found that the vast majority of Wyoming's flash floods coincided with the southwest U.S. monsoon season, taking place in July and August during the afternoon and evening hours. The circulation pattern over the western and central U.S. were similar several hours prior to heavy rainfalls. A primary trigger for Wyoming heavy thunderstorms was terrain-forced upward motion due to the easterly component of the surface winds.