Moisture Sources for Flash Floods in the United States

This study uses a recently published database of flash floods in the United States to determine the climatological moisture sources for extreme events. The database contains flooding events documented by the National Weather Service, the Severe Hazards Analysis and Verification Experiment conducted at the National Severe Storms Laboratory, and streamflow records from stations operated by the United States Geological Survey. Backward trajectories of air parcels are computed from numerical weather prediction model reanalysis data using a Lagrangian particle dispersion model for the events in this database. This approach elucidates the major synoptic-scale source regions of moisture for each flash flooding event. In addition, the roles of the heat and moisture budgets are examined in order to identify and quantify the role of terrestrial sources of moisture.