Earl carried sustained winds of 169 kmph and was a
Category 2 hurricane in the five-step Saffir-Simpson scale of intensity.
"Hurricane conditions are now spreading into the
Northern Leeward Islands and will spread westward into the Virgin Islands later
today," the hurricane center said in its 5 a.m. (0900 GMT) advisory.
"Earl is expected to become a major hurricane by
tonight or early Tuesday," it added.
The storm's center was 80 km east-northeast of the French
overseas island of St. Martin and moving north-northwest.
Hurricane warnings were in effect through the Caribbean,
including the US and British Virgin Islands, Antigua and Barbuda and the
British overseas territories of Montserrat and Anguilla.
Tropical storm conditions were expected to spread over
the US territory of Puerto Rico on Monday, with hurricane conditions possible
by evening.
The hurricane center warned of a storm surge, dangerous
waves and heavy rains that could cause flash flooding and mudslides in areas of
higher elevation.
Caribbean airline LIAT canceled 41 flights to several
destinations in the eastern Caribbean and shut down its reservation service
because of Earl's approach, according to a company statement.
Forecasters said Earl could affect the US East Coast
later this week.
"It looks like the storm will be east of the Bahamas
on Wednesday, east of Cape Hatteras on Thursday and then probably east of or
near Cape Cod and Long Island on Friday," Miami's WFOR-TV forecaster Jeff
Berardelli said on CBS radio.
In the North Atlantic, Hurricane Danielle, a major Category
4 storm last week, was barely a hurricane on Monday morning as its sustained
winds fell to 75 mph (121 kph). The storm was expected to lose its tropical
characteristics later in the day.
It was about 708 km south of Newfoundland.