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Tropical Storm Bill, the second storm of the Atlantic season, formed farther east and forecasters said they expect it to become a hurricane over the next several days.
The National Hurricane Center said Saturday night that Ana had maximum sustained winds near 40 mph and was moving west near 17 mph. It was about 710 miles east-southeast of the Leeward Islands and was not expected to strengthen in the next 24 hours.
A tropical storm watch means tropical storm conditions are possible, usually within 36 hours.
The government of the Netherland Antilles issued a watch for St. Maarten, Saba and St. Eustatius. The governments of Antigua and Barbuda issued watches for the British Virgin Islands and Montserrat, Antigua, Barbuda, St. Kitts, Nevis and Anguilla.
The Hurricane Center said people elsewhere in the Leeward Islands and Puerto Rico should also monitor Ana's progress.
Tropical Storm Bill also had maximum sustained winds near 40 mph and was moving west near 16 mph. It was expected to get stronger within the next day or so and was about 905 miles west-southwest of the Cape Verde Islands.
Meanwhile, Hurricane Guillermo was still swirling in the open Pacific but had weakened to a Category 2 storm with winds near 110 mph. Guillermo was expected to weaken further as it headed over cooler waters. It was moving west-northwest near 15 mph and was about 1,685 miles west of the southern tip of Mexico's Baja California peninsula.