Hurricane Erin rapidly strengthened offshore to a “catastrophic” Category 5 storm on Saturday, as rain lashed Caribbean islands and weather officials warned of possible flash floods and landslides.

Tropical Storm Erin has begun strengthening as it streaks west across the Atlantic and is on track to reach hurricane status as soon as Friday, prompting tropical storm watches in the northern Leeward Islands.

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,