(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 can'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.
What has Puerto Rico been advised to do? How far away is Hurricane Ana from the Leeward Islands? Which countries are advised to monitor storm's progress? What are the storm's max sustainable wind speeds What type of storm is Ana? How far from leeward islands is Ana? Where is Ana located? What are the maximum sustained winds of the storm? Which countries are advised to monitor storms progress
monitor the storm's progress. 730 miles (1,180 km) Virgin Islands and Puerto Rico 40 mph Tropical 730 miles (1,180 km) east-southeast the Caribbean 40 mph (65 kph), Puerto Rico
question: What has Puerto Rico been advised to do?, answer: monitor the storm's progress. | question: How far away is Hurricane Ana from the Leeward Islands?, answer: 730 miles (1,180 km) | question: Which countries are advised to monitor storm's progress?, answer: Virgin Islands and Puerto Rico | question: What are the storm's max sustainable wind speeds, answer: 40 mph | question: What type of storm is Ana?, answer: Tropical | question: How far from leeward islands is Ana?, answer: 730 miles (1,180 km) east-southeast | question: Where is Ana located?, answer: the Caribbean | question: What are the maximum sustained winds of the storm?, answer: 40 mph (65 kph), | question: Which countries are advised to monitor storms progress, answer: Puerto Rico