The storm, located 410 miles (655 kilometers) south-southwest of the southern tip of Baja California, posed no immediate threat to land, the US National Hurricane Center said.

At 1500 GMT, Miriam was moving toward the northwest at around 12 miles (19 kilometers) per hour.

The Miami-based storm watch center said it was possible that Miriam could strengthen further before gradually weakening sometime Tuesday, as it moves northward over cooler waters.