Forecasters at the National Hurricane Center in Miami said at 2 p.m., Dolly's sustained winds had increased to 70 mph with slightly higher gusts. When sustained winds surpass 74 mph, a storm becomes a Category 1 hurricane. The storm was centered about 195 miles southeast of Brownsville, Texas, moving northwest near 10 mph, forecasters said.

Tropical storm-force winds extended 160 miles from the center and the report said current conditions would mean a landfall likely as a hurricane Wednesday near the Mexican-U.S. border.

Mexico had tropical storm warnings posted from the U.S. border south to Rio San Fernando, while the Texas hurricane warning was from Brownsville north to Port O'Connor.

Elsewhere, Tropical Storm Cristobal veered farther from northeastern North American shores. Forecasters said the storm, centered about 280 miles south-southwest of Halifax, Nova Scotia, was moving northeast near 25 mph with 65 mph winds and higher gusts.

The Canadian Hurricane Center said the storm "will track far enough offshore to prevent strong winds from affecting land areas" although heavy surf and heavy rain had begun in the province.