(CNN)-- A tropical storm formed in the Pacific Ocean on Thursday morning and is expected to reach hurricane strength before it gets to Mexico's southwestern coast.
Tropical Storm Carlotta was about 430 miles (692 kilometers) southeast of Puerto Angel, Mexico, and 635 miles (1022 kilometers) from the resort town of Acapulco, the National Hurricane Center said.
The storm, with sustained winds near 40 mph (64 kph), was moving toward the northwest at about 10 mph (16 kph), the center said.
"Carlotta is expected to become a hurricane by the time it reaches the Pacific coast of Mexico on Friday," a Hurricane Center advisory said.
A hurricane watch is in effect for the Mexican coast from Barra de Tonala to Punta Maldonado.