Powerful Hurricane Erin has undergone a period of astonishingly rapid intensification — a phenomenon that has become far more common in recent years as the planet warms. It was a rare Category 5 for a time Saturday before becoming a Category 4,

Hurricane Erin is now a Category 5 storm, the highest on the class, rapidly intensifying overnight into early Saturday morning as it threatens the Leeward Islands and Puerto Rico, then will move along the U.