.FOR CALIFORNIANS it seemed like recognition. In 2015 a march of hurricanes, fed by atmospheric streams, killed at least 21 people and also created nearly $5bn-worth of damages across the condition. On February fourth this year the same sort of tornado again wreaked havoc. Hurricane-strength winds buffeted the main shore near Major Sur. In Los Angeles celebrities were saturated as they arrived at the Grammy awards' red carpet. Mansion houses in the Hollywood Hillsides were dealt with in mud. At the very least three people have died. What are atmospheric streams, and are they a threat beyond California?