What is an atmospherical river?

.FOR CALIFORNIANS it felt like du00e9ju00e0 vu. In 2013 a ceremony of storms, fed through atmospheric streams, gotten rid of a minimum of 21 individuals and resulted in nearly $5bn-worth of harm all over the state. On February 4th this year the same form of storm once again ravaged.

Hurricane-strength winds buffeted the core coast near Major Sur. In Los Angeles famous people were actually saturated as they reached the Grammy awards’ welcome mat. Estates in the Hollywood Hillsides were actually covered in mud.

At the very least 3 individuals have passed away. What are actually atmospheric streams, and also are they a risk past The golden state?