Forecasters say Miriam has rapidly strengthened into a Category 2 hurricane well off Mexico's Baja California peninsula, but poses no threat to land.
Forecasters at the National Hurricane Center in Miami said Miriam is packing top sustained winds of 105 mph (165 kph) and could become a major hurricane sometime later Monday. The hurricane formed a day earlier in the eastern Pacific and at 5 a.m. EDT was centered about 415 miles (665 kms) south-southwest of the southern tip of Baja California.
The center says Miriam was moving northwest near 13 mph (20 kph). No coastal watches or warnings are in effect.
In the open Atlantic, Tropical Storm Nadine weakened somewhat early Monday while meandering far from land. It had sustained winds of about 50 mph (85 kph).