inside-carlotta

Miami's National Hurricane Center says Tropical Storm Carlotta is expected to become a hurricane by the time it reaches Mexico's southern coast on Friday. (National Hurricane Center)

Tropical Storm Carlotta has formed in the Pacific south of Mexico and is expected to become a hurricane by tomorrow.

Carlotta's maximum sustained winds increased Thursday morning to nearly 70 km/h. The U.S. National Hurricane Center in Miami says additional strengthening is forecast and Carlotta is expected to become a hurricane by the time it reaches Mexico's southern coast on Friday.

A hurricane watch is in effect for Mexico's Pacific coast from Barra de Tonala to Punta Maldonado.

The tropical storm is centred 650 kilometres south-southeast of Puerto Angel, Mexico, and 965 kilometres southeast of Acapulco.

The storm is moving northwest near 17 km/h.

Tropical storm-force winds are extending outward up to 75 kilometres.