MIAMI (AP) — A third tropical storm has formed in the eastern Atlantic Ocean.

The National Hurricane Center in Miami said Saturday night that Tropical Storm Isaac was centered about 1,580 miles (2,540 kilometers) east of the Windward Islands.

There are no coastal watches or warnings in effect, but officials say it is expected to become a hurricane by Monday.

The storm's maximum sustained winds are 50 mph (85 kph) and it is moving west at 8 mph (13 kmh).