… In a study published earlier this year in Nature that looked at 40 years of water vapor, precipitation and wind speed observations, [former NOAA research scientist Wenhao] Dong and his co-authors found that wintertime atmospheric rivers are growing significantly more frequent and intense over the Eastern U.S. while diminishing over the West. … [S]tates such as Washington, Oregon and California have seen atmospheric river frequency decrease by nearly 4 percent per decade since 1980, the researchers found. This has led to long-term wintertime drying of the West Coast. … While the West is drying out overall, there is an increase in extreme precipitation events that are associated with catastrophic atmospheric rivers, Dong added.