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,

Erin’s sustained winds increased to 70 mph, just 4 mph shy of hurricane strength. The hurricane center said Erin should continue to strengthen through the weekend, when it should be moving near or north of the Leeward Islands, according to the official forecast path.