Weather forecasters say Tropical Storm Hilary has become a hurricane off Mexico's Pacific coast, and could strengthen into a major one by late Friday.

The U.S. National Hurricane Center said Thursday that the storm was 225 kilometers south-southeast of Acapulco, Mexico and moving northwest. Mexico has issued a tropical storm watch for its Pacific coast.

Forecasters also are watching newly-formed Tropical Storm Ophelia in the Atlantic. At last report, the hurricane center said the system was 1,570 kilometers east of the Leeward Islands, moving to the west with winds up to 100 kilometers per hour.