MIAMI The first two named tropical storms of the 2009 Atlantic hurricane season, Ana and Bill, formed over the Atlantic on Saturday and moved westward, and the National Hurricane Center said Bill was expected to become a hurricane in 3-4 days.
At 1700 EDT (2100 GMT), Bill was located about 820 miles west-southwest of the Cape Verde Islands and was moving west with maximum sustained winds near 40 miles per hour, the NHC said.
"Strengthening is indicated and Bill is expected to become a hurricane in three to four days," it said, adding forecasts showed this would take place when the storm was very near the Northern Leeward Islands. The five-day forecast track showed it could threaten Puerto Rico and the Bahamas.
Tropical storms become hurricanes when their top sustained winds reach 74 mph.
Earlier on Saturday, the first named tropical storm of the 2009 Atlantic season, Ana, formed. It was heading toward the Leeward Islands, and could also threaten the Virgin Islands and Puerto Rico.
The NHC said some forecasts of Ana's likely track showed it could pass over or near the southern Florida peninsula within five days, but initial projections did not show this storm developing into a full-blown hurricane in that time.
With maximum sustained winds near 40 miles per hour, Ana was located at 1700 EDT (2100 GMT) about 805 miles east-southeast of the Leeward Islands.
The NHC said the government of the Netherland Antilles had issued a tropical storm watch for St. Maarten, Saba and St. Eustatius.
The 2009 hurricane season, which runs from June through November, has gotten off to a late start. By this time last year, there had already been five named storms in the Atlantic basin.
The National Oceanic and Atmospheric Administration has predicted this year's Atlantic hurricane season will see normal to below-normal activity, with seven to 11 tropical storms and three to six hurricanes.
Energy traders watch for storms that could enter the Gulf of Mexico and threaten U.S. oil and natural gas platforms and refineries along the coast. Commodities traders watch storms that could hit crops such as citrus and cotton in Florida and other states along the coast to Texas.
(Writing by Alan Elsner and Pascal Fletcher, editing by Todd Eastham)