Tropical Storm Earl strengthened rapidly Tuesday and was expected to become the season's third hurricane as it moved on a track toward the U.S. Gulf Coast.

The storm's clouds nearly filled the gulf, and one computer model projected "explosive intensification," the National Hurricane Center said.By late morning, the storm's highest sustained wind was 60 mph, up from 40 mph late Monday. Its center was about 350 miles south-southwest of New Orleans, and it was moving north at 6 mph.

Earl was expected to build into a hurricane by Wednesday and could come ashore Friday with 90 mph wind. It was expected to hit land somewhere from Texas to the Florida Panhandle, with the likeliest striking point near New Iberia, La., meteorologists said.

Elsewhere, a tropical storm watch was posted for Bermuda as Hurricane Danielle rolled across the Atlantic with 100-mph wind. Danielle was about 405 miles west of Bermuda and was expected to turn toward the northeast.