Catastrophic flooding and atmospheric circulation anomalies, ( USA)

An analysis of the atmospheric circulation patterns associated with twenty-one catastrophic floods in the conterminous United States demonstrates that each flood can be linked to anomalous patterns of circulation. Extreme regional floods over broad areas evolve from different types of large-scale anomalous behavior: uncommon locations of typical circulation features, unusual combinations of atmospheric processes, rare configurations in circulation patterns, and exceptional persistence of the same circulation pattern. Extreme local flash floods over small drainage areas can be classified into synoptic categories of existing flash-flood forecasting schemes, and in addition, these small-scale catastrophic events exhibit sensitivity to large-scale circulation anomalies. -from Author