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Publication Date
13 April 2024

Definitive Evidence that Atmospheric Rivers East of the Rockies are the Same as their West Coast Counterparts

Atmospheric rivers in the eastern half of the U.S. systematically occur with midlatitude cyclones.
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An atmospheric river (AR) over the midwestern United States within a baroclinic wave:  AR probability (colored contours; lowest contour is 90%, spacing is logarithmic up to 100%) and 500 mb geopotential heights (gray contours; from 4500 m to 6000 m in 50 m increments) overlaid on geostationary satellite imagery from GOES-16 on 2017-04-30 15Z.  Satellite imagery was produced using code generously provided by Brian Blaylock's GOES-2-go python package (, and geopotential height data come from the ERA5 reanalysis provided by the NCAR RDA. Image created by Dr. Travis A. O'Brien.


A new study by researchers at Indiana University and Lawrence Berkeley Lab shows that atmospheric rivers (ARs) in the eastern half of the U.S. systematically occur in conjunction with large-scale weather patterns known as midlatitude cyclones.


Atmospheric rivers and their impacts are well-studied on the West Coast of the U.S., and there is increasing evidence that they are important for the eastern half of the country, too. It was not clear, however, whether western and eastern U.S. ARs have the same meteorological drivers. This study demonstrated that knowledge about western U.S. ARs can translate across the U.S.


Atmospheric rivers (ARs) are a weather pattern that brings high amounts of atmospheric water and winds in a relatively narrow region. ARs are typically considered a “West Coast” phenomenon, largely because the majority of the scientific research on ARs has focused on ARs in western coastal regions: particularly the western United States (US). ARs occur in continental interiors, but there has been some debate about whether these ARs represent the same type of weather as those in western coastal regions. This paper uses two objective methods for identifying ARs and finds times when ARs are present in three locations in the eastern half of the US: Norman, OK, Bloomington, IN, and Washington, DC. Examination of weather conditions during these AR times shows remarkable similarity to conditions associated with west coast ARs. This gives strong evidence that ARs do occur in the eastern half of the US. This result is important because it suggests that ARs may be important for water resources and extreme weather in the eastern half of the US, just as they are in the western US. This result also suggests that ARs may be important for water resources and extremes in other continental interiors. 

Point of Contact
Travis A. O'Brien
Indiana University
Lawrence Berkeley National Laboratory
Funding Program Area(s)
Additional Resources:
NERSC (National Energy Research Scientific Computing Center)