MIAMI -

Tropical Storm Dorian became a tropical wave Saturday as it pushed westward across the Atlantic toward the Caribbean islands.

At 5 p.m. Saturday, the storm was about 550 miles east of the northern Leeward Islands with maximum sustained winds near 40 mph, according to the National Hurricane Center in Miami. It was moving west at 24 mph.

Read: Max Mayfield on Dorian | Local 10 Hurricane Headquarters

National Weather Service meteorologist David Sanchez told The Associated Press that some rain and rough ocean conditions are expected on Monday in Puerto Rico.

There are no coastal watches or warnings in effect.

Dorian is the fourth named storm of the Atlantic Hurricane Season.