MIAMI — A weather system swirling off the coast of western Mexico has developed into a tropical storm. That is according to the National Hurricane Center.

Tropical Storm Alvin was located about 670 miles (1,080 kilometers) south-southeast of the southern tip of Baja California. Maximum sustained winds were clocked at 40 mph (65 kph). It was moving northwest at 10 mph (17 kph).

There were no coastal watches or warnings in effect at 10 a.m. EDT, the hurricane center said.

The storm was expected to strengthen late Thursday, then weaken late Friday.