Atmospheric rivers and the connection to heavy rainfall events in the southeastern U.S. compared to the U.S. West Coast

Many studies have documented the key role of atmospheric rivers (ARs) in extreme precipitation and flooding in the western U.S., however comparatively little research has been conducted on this topic in the eastern U.S. Evidence suggests that events such as the severe flooding in Tennessee in May 2010 have been partially driven by the presence of an AR, but a robust study of the linkage between AR conditions and eastern U.S. precipitation remains elusive. An extreme precipitation climatology produced as part of the NOAA Hydrometeorology Testbed (HMT) 2013 – 2014 pilot project in the Southeast U.S. (HMT-SEPS) has identified a collection of heavy precipitation cases such that the correlation between extreme rainfall and AR conditions can be quantified. A newly-developed AR detection tool (ARDT) based on integrated water vapor transport (IVT) is tested for the southeastern U.S. (SEUS), and the results are compared to a subset of heavy precipitation cases. ARDT performance in the SEUS is also compared to that in the western U.S. in order to determine the tool's utility for pinpointing precipitation associated with ARs. Such a comparison is of particular interest given the generally higher background moisture environment of the SEUS and the comparatively more diverse array of precipitation generation mechanisms (as opposed to generally drier background states and more orographically-focused precipitation in western U.S. AR environments.)

This presentation will describe the linkage between identified ARs and known heavy precipitation events in the SEUS, as well as compare the types and frequencies of heavy precipitation events that are not linked to AR conditions in this region. A comparison of forecast skill for events that are and are not linked ARs will also be presented. A primary objective of this investigation is to determine whether defining synoptic-scale moisture transport features as ARs in the SEUS is dynamically meaningful and/or can provide potential operational or applied forecast benefit.