There are many hydrologic and meteorological variables that can affect the characteristics of flooding in a basin. Knowing the relative roles of the different variables will lead to improvements in prediction of and help to constrain climate projections of flood events. Therefore, this analysis examines how aspects of basin hydrology and the atmosphere relate to flood probability. There are 3 separate regions of focus for this analysis within the United States: The Northeast US, the Midwest and the Pacific Northwest. The first part of the analysis is focused on rainfall volume and the spatial footprint of precipitation extremes, defined here as: Simultaneous Heavy Precipitation Events (SHPEs). Based on a compositing analysis of geopotential height anomalies and precipitable water, we find that SHPEs are often associated with an extratropical cyclone interacting with a downstream high-pressure system. The overlap between SHPE spatial extents and Hydro-Climatic Data Network (HCDN) watersheds are used to analyze how streamflow levels in specific drainage basins react after a SHPE event, however the resulting relationship is quite noisy. This suggests that the characteristics of the atmosphere provide limited predictability. For some regions, this conditional sorting analysis provides improved predictability of the flooding.

The National Oceanic and Atmospheric Administration – Cooperative Science Center for Earth System Sciences and Remote Sensing Technologies (NOAA-CESSRST) under the Cooperative Agreement Grant #: NA16SEC4810008. The authors would like to thank The City College of New York, NOAA-CESSRST program and NOAA Office of Education, Educational Partnership Program for full fellowship support for Carolien Mossel.