A "bomb cyclone" and an "atmospheric river" are poised to deliver intense ... and "cyclogenesis," which describes the formation of cyclones—low-pressure systems that rotate counterclockwise ...

"The formation of this rapidly strengthening ... the weather service said. An atmospheric river prompted a high-risk warning for excessive rainfall along the Northern California coast.

including an outbreak of tornados expected from the Southern Plains to the Southeast and an atmospheric river in the Northwest. Millions of people were under tornado watches on Saturday in eastern ...