Hurricane Bill still growing, should miss U.S.

Hurricane Bill is pictured moving through the Atlantic Ocean, more than 1,160 miles east of the Lesser Antilles islands of the Caribbean, in this satellite image taken on August 17, 2009.

MIAMI (Reuters) - Hurricane Bill trekked west-northwest over the open Atlantic on Tuesday and was poised to develop into a major hurricane, but its forecast path seemed likely to miss the U.S. East Coast.

The U.S. National Hurricane Center said that Bill, the Atlantic season's first hurricane, was packing top winds near 110 miles per hour (175 km per hour), just one mph short of turning into a Category 3 hurricane.

"Bill is expected to become a major hurricane tonight or Wednesday," the NHC said, saying its center was located at 1700 EDT (2100 GMT) about 635 miles east of the Caribbean Leeward Islands.

The hurricane center, which sent a plane to probe the cyclone's swirling cloud mass on Tuesday, forecast Bill could strengthen to a Category 4 hurricane in the next 24 hours.

Category 3, 4 and 5 storms on the Saffir-Simpson intensity scale are those likely to cause the most damage.

Bill posed no threat to the U.S. Gulf of Mexico oil-producing area. Its curving path was expected to take it just west of Bermuda, a mid-Atlantic British territory and reinsurance capital, by Saturday.

Bermuda authorities warned residents to be prepared.

Hurricane expert Jeff Masters, founder of the Weather Underground website, said he expected Bill to move between Bermuda and the U.S. East Coast toward Canada's Maritime Provinces.

"I think the likely main impact (on the U.S. coast) is going to be beach erosion and coastal waves," he said. "Direct impacts are unlikely."

Bill will encounter energy-sapping cool water when it reaches the latitude of North Carolina but could still be a Category 1 hurricane near Nova Scotia and Newfoundland, Masters said.

The National Hurricane Center notes that long-range track forecasts -- from three to five days in advance -- have average errors of several hundred miles.

Meanwhile, energy traders were keeping an eye on the remnants of Tropical Storm Ana, which was producing thunderstorms over Haiti, Cuba and the Bahamas.

The NHC forecast that the storm front had a low chance -- less than 30 percent -- of becoming a tropical cyclone again over the next 48 hours.

One forecaster, AccuWeather.com, said it was unlikely but possible the system could regenerate over the eastern Gulf later in the week. Some forecasters noted that Ana had already regenerated once.

Energy markets watch storms in the Gulf of Mexico closely because the region produces a quarter of U.S. oil and 15 percent of its natural gas.

(Additional reporting by Pascal Fletcher and Scott DiSavino; Editing by Pascal Fletcher)