Tropical Storm Florence intensified Saturday morning, packing winds nearing 70 mph as it moved through the open Atlantic on a path toward Bermuda, threatening to quickly become hurricane.

Florence was expected to reach the tiny British territory Monday, but it was too early to tell whether it will make a direct hit, according to forecasters at the National Hurricane Center in Miami.

“Even if the center misses Bermuda by a couple hundred miles, this is a very large storm so there’s likely to be some effect,” said Mark Willis, a meteorologist at the center. “If not the strong winds, there will definitely be some rough surf.”

The storm was expected to veer away from the U.S. coast as it turns north toward Bermuda, but forecasters said its large size could create high surf and rip currents along parts of East Coast.

Large ocean swells Saturday were affecting Bermuda as well as the northern coasts of Caribbean islands including Puerto Rico and the U.S. Virgin Islands, the hurricane center said.

Bermuda has issued a hurricane watch and a tropical storm warning, and the government urged the territory’s 65,000 residents to take precautions. Florence was expected to reach hurricane status later Saturday with winds of at least 74 mph.

“The public is encouraged to stock up on normal hurricane supplies and to secure their homes, lawn furniture and any other loose items which could be affected by high winds,” said Derrick Burgess, minister of public safety.

A line of customers snaked through the Masters hardware store in Hamilton, which sold out of lanterns by Friday afternoon. Carolyn Wagensveld, who was stocking up on candles, said she arrived from Toronto on Thursday to take a teaching job and was looking to locals for guidance.

“I’m a little nervous. But the islanders don’t seem to worried, so I’m not too worried,” she said.

Another customer, Colette Lightbourne, said storm preparations were a familiar routine.

“It’s happened so many times before, we’re used to it,” she said. “Everyone will be buying their supplies today and clearing their yards.”

The storm’s sustained winds strengthened to nearly 70 mph Saturday. Tropical storm force wind extended up to 345 miles from Florence’s center.

At 2 p.m. EDT, the storm was centered about 500 miles south of Bermuda, where it has started to rain. Florence was moving northwest at about 13 mph.

“We don’t know exactly how strong it’s going to get, but this is something to which people should pay close attention,” said Lou McNally, of the Bermuda Weather Service. “Preparations should be well under way.”

Bermuda, a wealthy island chain 640 miles east of the U.S. coast, requires newly built houses to withstand sustained winds of 110 mph. It also has a sturdy infrastructure with many of its power and phone lines underground.

Hurricane Fabian killed four people when it struck in 2003 as the strongest storm to hit Bermuda in 50 years. Fabian, a Category 3 hurricane with 120 mph winds, tore the roofs off several homes and left many of Bermuda’s famed golf courses in ruins.

Authorities said they were moving emergency personnel across a causeway linking the main island with St. George’s parish to be on hand for floods or fires. Part of the causeway was swept away when Fabian struck.

Florence follows on the heels of Tropical Storm Ernesto, which was briefly the season’s first hurricane before weakening and drenching the East Coast last week. The storm was blamed for nine deaths in the United States and two in Haiti.

Florence developed in the peak of hurricane season over warm Atlantic water, the source of energy for storm development this time of year. While those waters are warm enough to spur storm intensification, forecasters said they are not as warm as last year’s storm season, which had a record 28 named storms and 15 hurricanes, including Katrina.

The 2006 Atlantic hurricane season has not been as rough as initially feared. The National Hurricane Center lowered its forecast in August to between 12 and 15 named storms and seven to nine hurricanes.

On the Net:

U.S. National Hurricane Center: http://www.nhc.noaa.gov