Hilary, with top winds of 135 miles (215 kilometers) per hour, up from 105 mph earlier today, was about 85 miles south- southeast of Acapulco and moving west-northwest at 9 mph.
“Some additional strengthening is possible on Friday,” the center said in an advisory at about 8 p.m. Eastern time. “The core of Hilary will continue to move parallel to the southwest coast of Mexico, but any deviation to the north of the track could bring stronger winds to the coast.”
Mexico’s government has posted a tropical-storm warning from Lagunas de Chacahua to Punta San Telmo and a tropical-storm watch from Punta San Telmo to the coastal resort of Manzanillo, according to the U.S. center. Winds of at least 39 mph, tropical storm strength, are reaching the coast and as much as 10 inches (25 centimeters) of rain may fall in some areas.
Hilary’s top winds make it a Category 4 cyclone on the five-step Saffir-Simpson scale, the center said. A storm is considered a major hurricane when its winds top 111 mph, the threshold for Category 3 status.
While Hilary may be strong, it’s a small storm, the center said. Hurricane-force winds, those of at least 74 mph, extend only 25 miles from its core.
In the Atlantic, Tropical Storm Ophelia, the 15th named system of the season, was about 820 miles east-southeast of the Leeward Islands, the center said. The system, moving west at 12 mph, weakened to sustained winds of 50 mph from 65 mph.
Ophelia is expected to degenerate in the next two days as it encounters strong upper-level winds, the center said. The hurricane center’s current track forecast predicts Ophelia will veer north of Puerto Rico and into the mid-Atlantic.