NEW SMYRNA BEACH, Fla. — Tropical Storm Ophelia strengthened into a hurricane as it stalled 70 miles off the northeast Florida coast yesterday, churning up waves that caused beach erosion and drenching Kennedy Space Center with rain.

Last night, Ophelia had top sustained winds of 75 mph, just over the threshold to be classified as a hurricane, forecasters at the National Hurricane Center said.

But forecasters said it was still unclear where Ophelia was headed.

If it hits Florida, it would become the third hurricane to strike the state this year and the seventh in the last 13 months.

Downpours from earlier storms had caused flooding in Flagler County, raising anxiety about the effect of more rain. Authorities shut down a mile-long stretch of beachfront road in Flagler Beach so transportation workers could shore it up with sand and boulders.

"The storm is eating up our dunes," said Carl Laundrie, communications manager for Flagler County.

As a precaution, 14 Navy ships at the Naval Station Mayport in Jacksonville headed to sea.

Two shelters in Flagler County were readied. Neighboring Volusia County opened three shelters but later closed them because just 12 people showed up.

"We know from last year these storms can do an about-face. We are not out of the woods unless this storm moves well away from Volusia's coast," said Dave Byron, spokesman for Volusia County.

At 8 p.m., Ophelia was centered about 75 miles east-northeast of Cape Canaveral, with hurricane-force winds stretching up to 15 miles from the center.

Hurricane specialist Jack Beven said Ophelia should start moving north or northeast — away from land — within a day or so. However, it could curl back early next week and slam north Florida or Georgia as a Category 1 hurricane.

Storm warnings or watches were posted for Florida's east coast from Sebastian Inlet to Fernandina Beach.

Officials at NASA were keeping an eye on Ophelia. Last summer, the space agency's launch and landing site took the brunt of three hurricanes, which punched big holes into the massive building where shuttles are attached to their booster rockets and fuel tanks.

Ophelia was the seventh hurricane of the Atlantic season, which began June 1 and ends Nov. 30. The peak season typically occurs from the end of last month through mid-September.