What is actually an atmospheric stream?

.FOR CALIFORNIANS it felt like remembrance. In 2014 a procession of storms, fed through atmospheric streams, killed at least 21 folks as well as led to nearly $5bn-worth of harm around the condition. On February 4th this year the very same kind of hurricane again ravaged.

Hurricane-strength winds buffeted the central coastline near Big Sur. In Los Angeles celebrities were saturated as they arrived at the Grammy awards’ red carpet. Manors in the Hollywood Hillsides were actually covered in mud.

A minimum of 3 people have passed away. What are climatic streams, and also are they a danger beyond California?