Atmospheric Rivers and Flood-Related Watches, Warnings, and Advisories Issued by the NWS over the Northeast United States: 2008–17

Atmospheric rivers (ARs) are known to influence the frequency of extreme precipitation events, floods, and flash floods across the western U.S. and other locations across the globe. The goal of this poster is to identify the relationship between ARs and the potential for high-impact weather events associated with floods and flash floods over the Northeast U.S. This relationship is illustrated via comparison of an AR catalog over the Northeast U.S. and watches, warnings, and advisories (WWAs) issued by the National Weather Service. The AR catalog was subjectively created by examining maps of integrated water vapor transport (IVT) created from the NASA MERRA Reanalysis dataset for (1) regions of IVT with magnitudes >250 kg/(m*s) in the Northeast domain (38–48˚N and 80–66°W), (2) with a spatial scale of greater than 2000 km long and less than 1000 km wide (or 2:1 ratio), and (3) associated with an extratropical cyclone. The AR catalog identified an average of ~107 ARs per year that met this definition over the Northeast U.S. The AR catalog was then compared with a 2008–2017 daily WWA catalog of floods, flash floods, and areal floods for public forecast zones (PFZ) over the Northeast U.S. The comparison identified that 50–93% of days with at least one WWA in any given PFZ occurred on the same day as an AR located over the same PFZ. Although WWA days are likely to occur with ARs (i.e., >50% of the time), not all Northeast U.S. ARs produce WWAs.