Atmospheric Rivers Are a Frequent Source of Moisture Transport in Severe Convective Storm Environments

Atmospheric rivers (ARs) are well known for their contributions to precipitation and flooding across the U.S. The present study explores the relationship between ARs and the potential for severe thunderstorms and tornadoes over the U.S. in both the warm and cool seasons during a 20-year period from 2004 to 2023. A statistical analysis of severe thunderstorm and tornado warnings issued by the National Weather Service and AR events demonstrates that a majority of warnings over the Southeastern and Eastern U.S. are associated with ARs, especially tornado warnings. Conversely, given an AR event, a minority of AR events feature severe thunderstorm warnings or tornado warnings, with higher fractions in the warm season except for tornado warnings over the Southeastern U.S. It is concluded that ARs appear as a practically necessary, but not sufficient, factor related to the potential for severe convective storms, especially the issuance of tornado warnings in the cool season.