( CNN ) -- Tropical Storm Ana threatened the Caribbean on Saturday , but it was too early to know how much trouble the first named storm of the 2009 Atlantic hurricane season might cause . Forecasters expect Tropical Storm Ana to hit the Leeward Islands on Monday . Ana formed overnight and was expected to gain strength as it moved west toward the Leeward Islands , where forecasters expect it to hit on Monday . The Dutch Antilles issued a storm watch for St. Maarten , Saba and St. Eustatius , meaning tropical storm conditions are expected in the islands within 36 hours , according to the Miami , Florida-based National Hurricane Center . For now , the center has advised the Virgin Islands and Puerto Rico to monitor the storm 's progress . As of 8 p.m . ET , Ana was about 730 miles ( 1,180 km ) east-southeast of the Leeward Islands , according to the hurricane center . Ana , with maximum sustained winds of 40 mph ( 65 kph ) , was moving west at about 17 mph ( 28 kph ) , the center reported . The storm is expected to turn west-northwest over the next few days , the center said . Ana may eventually hit Haiti and the Dominican Republic , but forecasters ca n't say whether Ana will strike the continental U.S. Further east in the Atlantic , Tropical Storm Bill has developed and is expected to become a hurricane Wednesday . Forecasters say Bill could evolve into a Category 3 hurricane as it approaches the Leeward Islands by Wednesday or Thursday . Bill was about 820 miles ( 1,320 km ) west-southwest of the Cape Verde islands at 5 p.m . ET .
NEW : Ana is 730 miles east of Leeward Islands , moving west at 17mph . The storm will be a hurricane by the time it makes landfall on Dominica and Jamaica later this afternoon or early evening. Storm has maximum sustained winds of 40 mph , hurricane center says .