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,

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.

"Erin will be a large and powerful hurricane over the southwestern Atlantic Ocean this weekend," the National Hurricane Center said.

As Erin continues to churn over very warm water, the storm will gain quick momentum and will likely become the first major hurricane (a category 3, 4 or 5 storm) as early as this weekend as it passes to the north of Puerto Rico.

Erin developed in the eastern Atlantic, moving westward from the Cabo Verde Islands at about 20 mph (32 km/h). Infrared sensors on NOAA's GOES-19 satellite reveal colder cloud tops and deep convection near the center — signs of a strengthening system feeding on warm ocean waters.