What is actually an atmospheric waterway?

.FOR CALIFORNIANS it believed that recognition. In 2015 a parade of storms, sustained by climatic rivers, eliminated at least 21 folks and resulted in nearly $5bn-worth of harm across the condition. On February fourth this year the very same type of storm once again ravaged.

Hurricane-strength winds buffeted the main coastline near Significant Sur. In Los Angeles celebrities were saturated as they got to the Grammy honors’ ceremony. Mansion houses in the Hollywood Hills were covered in dirt.

At least 3 individuals have died. What are atmospherical waterways, and are they a hazard beyond California?