Atmospheric Rivers and the Connection to Heavy Rainfall Events in the Southeastern U.S.

Abstract:

Many studies have documented the key role of atmospheric rivers (ARs) in extreme precipitation and flooding in the western U.S., however very 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, and that AR conditions may also have contributed to the “Snowmageddon” blizzard that struck the mid-Atlantic region in 2010. However, 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’s (HMT’s) most recent pilot project in the Southeast U.S. has identified a collection of heavy precipitation cases in which AR conditions are likely to have been a driving force of the precipitation in this region. A newly-developed AR detection tool (ARDT) based on integrated vapor transport (IVT) is being tested for the Southeast U.S. region and a subset of precipitation cases. ARDT performance is also compared to that of the western United States in order to determine the tool’s utility for pinpointing precipitation in the eastern U.S.’s environment of generally higher background moisture and 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 detail the linkage between identified ARs and known heavy precipitation events in the southeastern U.S., as well as compare the types and frequencies of heavy precipitation events that are not linked to AR conditions in this region. A primary objective of this investigation is to determine whether defining synoptic-scale moisture transport features as ARs in the eastern U.S. can provide potential operational or applied forecast benefit.