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 is now a rare Category 5, churning through the Atlantic Ocean north of the Caribbean.

A westward-moving tropical wave could produce an area of low pressure in the tropical Atlantic late in the week of Aug. 18, the hurricane center said on Aug. 16. The center shows a 20% chance of storm formation over the next week.