Hurricane Earl intensified Tuesday as it roared over the Atlantic Ocean, hammering the northeastern Caribbean with high winds and heavy rain.

The storm battered the U.S. and British Virgin islands, Puerto Rico and Antigua, causing flooding in low-lying areas and damaging homes on several small Caribbean islands. Several countries and territories reported power outages, cruise ships were diverted and flights cancelled across the region.

The U.S. National Weather Service's hurricane centre is forecasting that the storm will hit the east coast of the United States late Thursday before curving north and possibly side-swiping Atlantic Canada.

"Any small shift in the track could dramatically alter whether it makes landfall or whether it remains over the open ocean," said Wallace Hogsett, a meteorologist at the centre.

Tropical storm conditions were expected to spread into the Turks and Caicos by Tuesday afternoon, with a potential for above normal tides and dangerous tides. The territory was under a tropical warning and a tropical storm watch was in effect for the southeastern Bahamas.

Islanders on the Turks and Caicos pulled boats ashore and packed supermarkets as Earl howled over open seas toward the British territories on its way to the U.S. eastern coast.

The hurricane, with maximum sustained winds of 215 kilometres per hour, was expected to remain over the open ocean as it turns north and runs parallel to the U.S. coast, potentially reaching the North Carolina coastal region by Friday.

"There is still considerable uncertainty as to how close the hurricane will come to the U.S. East Coast," the U.S. National Hurricane Center in Miami said in a bulletin Tuesday.

Meteorologist Jay Anderson told CTV's Canada AM that the storm is barrelling into an already complicated weather picture in Atlantic Canada, which has been hit by clashing warm and cold fronts this week.

"It's actually a bit of a traffic jam on the East Coast … you've got a hurricane coming up from the south (into) a low and cold front. But the hurricane has the right of way."

Anderson said this year's more intense hurricane season is being driven by warmer-than-usual water temperatures in the central Atlantic, where the massive storms are born.

"So we're building stronger hurricanes and we're building more of them," he said. "And we're coming into the maximum of the hurricane season right now."

Earl is expected to drop to Category 2 strength by the time it reaches Nova Scotia at around dawn on Saturday.

But that does not diminish the danger. A Category 2 storm can pack winds of 150 to 175 kilometres per hour and a storm surge of water more than two metres high.

Hurricane Juan, a Category 2 hurricane, caused extensive damage when it tore through central Nova Scotia in September 2003.

The hurricane centre said it was too early to say what effect Earl could have in the U.S., but warned it could at least kick up dangerous rip currents. A surfer died in Florida and a Maryland swimmer has been missing since Saturday in waves spawned by former Hurricane Danielle, which weakened to a tropical storm Monday far out in the north Atlantic.

Craig Fugate, administrator of the U.S. Federal Emergency Management Agency, said Earl's approach ought to serve as a reminder for coastal regions to update their evacuation plans.

"It wouldn't take much to have the storm come ashore somewhere on the coast," Fugate said. "The message is for everyone to pay attention."

The rapid development of Earl, which only became a hurricane Sunday, took some Caribbean islanders and tourists by surprise.

Wind was already rattling the walls of Lila Elly Ali's wooden house on Anegada, the northernmost of the British Virgin Islands, when she and her son went out to nail the doors shut Monday.

"They say the eye of the storm is supposed to come close to us, so we've just got to pray. Everyone here is keeping in touch, listening to the radio," the 58-year-old told The Associated Press by phone from the island of 280 people.

There were reports of roofs torn from homes on Anegada, but the extent of damage across the Virgin Islands was still not clear Monday night. Emergency officials said they had no immediate reports of any fatalities or serious injuries.

In Anguilla, several utility poles were down and a couple of roofs had blown away, but it was still too dangerous to go out and assess the full extent of damage, said Martin Gussie, a police officer.

In St. Maarten, sand and debris littered the streets, and winds knocked down trees and electricity poles and damaged roofs. But police spokesman Ricardo Henson said there was no extensive damage to property.

In Antigua, at least one home was destroyed but there were no reports of serious injuries. Gov. Gen. Dame Louise Agnetha Lake-Tack declared Monday a public holiday to keep islanders off the road and give them a chance to clean up.

An estimated 10 to 20 centimetres of rain were forecast to fall on islands in the hurricane's path.

Early Tuesday, Earl was about 240 kilometres north-northwest of Puerto Rico's capital, San Juan, and moving west-northwest at 20 kilometres per hour, according to the hurricane centre. Hurricane-force winds extended outward up to 110 kilometres from its centre.

With files from The Associated Press