A hurricane watch is in effect for Anguilla, St Maarten, St Martin and St Barthelemy.
A tropical storm warning is in effect for Dominica, Anguilla, St Maarten, St Martin, St Barthelemy, Saba and St Eustatius.
A tropical storm watch is in effect for Barbados and Martinique.
The US National Hurricane Center (NHC) at 11 am said the centre of Hurricane Tammy was located near latitude 14.1 North, longitude 58.6 West.
Tammy is moving toward the west-northwest near 7 mph (11 km/h), and this general motion is expected to continue through this afternoon.
A turn toward the northwest is anticipated by this evening, followed by a north-northwestward and northward turn Saturday night through Sunday night.
On the forecast track, the centre of Tammy will move near or over portions of the Leeward Islands tonight and on Saturday, and then move north of the northern Leeward Islands on Sunday.
Data from NOAA and Air Force Reserve reconnaissance aircraft indicate that the maximum sustained winds are near 75 mph (120 km/h) with higher gusts. Gradual strengthening is forecast during the next couple of days, and Tammy is expected to be a hurricane while it moves near or over portions of the Leeward Islands.
Hurricane-force winds extend outward up to 25 miles (35 km) from the centre and tropical-storm-force winds extend outward up to 140 miles (220 km).
HAZARDS AFFECTING LAND
WIND: Tropical storm conditions are expected within the tropical storm warning area beginning later today or tonight. Hurricane conditions are expected in the hurricane warning area by late tonight or early Saturday. Hurricane conditions are possible in the hurricane watch area in the Leeward Islands on Saturday.
Tropical storm conditions are possible within the tropical storm watch area beginning later today.
RAINFALL: Tammy is expected to produce the following storm total rainfall:
Leeward Islands: 4 to 8 inches with maximum amounts of 12 inches
Northern Windward Islands: 2 to 4 inches with maximum amounts of 6 inches
British and US Virgin Islands into eastern Puerto Rico: 1 to 2 inches with maximum amounts of 4 inches
These rains may produce isolated flash and urban flooding, along with isolated mudslides in areas of higher terrain.
STORM SURGE: Storm surge could raise water levels by as much as 1 to 3 feet above normal tide levels near where the centre of Tammy moves across the Leeward Islands. Near the coast, the surge will be accompanied by large and dangerous waves.
SURF: Swells generated by Tammy will continue to affect portions of the Lesser Antilles during the next few days. These swells are likely to cause life-threatening surf and rip current conditions.
The NHC will issue its next intermediate advisory at 2 pm and complete advisory at 5 pm.