The first hurricane of the Atlantic season was a large and dangerous storm, packing 100 mph winds early Friday. Its center was in between St. Lucia and Martinique, two eastern Caribbean islands less than 50 miles apart, according to the National Hurricane Center in Miami.

St. Lucia's acting prime minister, Stephenson King, announced that the country's two commercial airports were closing Thursday night as the storm's outer bands began moving through the islands. Martinique's main airport was also closed.

"We may not be spared on this occasion as it appears that we are likely to experience the worst," King said.

The Category 2 hurricane was expected to intensify as it enters the warm waters of the Caribbean -- heading toward Jamaica.

It was too early to tell whether the storm would eventually strike the United States, but officials were gearing up for the possibility of the season's most severe storm yet.

"It's so far out, but it's not too early to start preparing," said Katherine Cesinger, a spokeswoman for Texas Gov. Rick Perry.

About 300 American medical students from Dominica's Ross University were stranded at the island's airport Thursday until family members hired private planes, said Dr. Mauricio Gomez, from the UCLA Medical Center in California, whose fiancee was among the students. Most arrived in Puerto Rico to await flights on Friday bound for the United States, Gomez said.

Hotels in Dominica and Martinique moved tourists from seaside rooms.

At the Jungle Bay Resort & Spa, on Dominica's Atlantic coast, about 18 guests spent Thursday night in a reinforced steel-and-concrete shelter, hotel spokeswoman Laura Ell said.

"Everyone's very calm but taking it seriously," she said.

Martinique officials set up cots at schoolhouse shelters while residents lined up at gas stations and emptied supermarket shelves.

"It's the first time I've seen this, all our water supply completely gone in less than two hours," said Jean Claude, a supermarket manager.

The government also canceled commemoration events planned for the 152 Martinique residents who died in a plane crash a year ago.

In St. Lucia, radio and television advisories urged people to stock up on canned food and fill their cars with gasoline. Volunteers knocked on doors to make sure people knew about the storm.

The National Hurricane Center said Dean would likely be a dangerous Category 3 hurricane by the time it reaches the central Caribbean. Forecasters say it appeared to be heading south of Puerto Rico, the U.S. Virgin Islands and the Dominican Republic and Haiti, which share the island of Hispaniola.

As it approaches the Mexican resort town of Cancun, on the Yucatan Peninsula, on Tuesday it could be an extremely dangerous Category 4 hurricane, the hurricane center said.

It predicted storm surge flooding at 2 to 4 feet above normal tide levels near the center of Dean as it passes over the Lesser Antilles and total possible rainfalls of 7 inches in mountainous areas.

At 5 a.m. EDT, hurricane warnings were in effect for the islands of St. Lucia, Martinique, Dominica and Guadeloupe.

Tropical storm warnings have been issued for the U.S. Virgin Islands, the British Virgin Islands, Puerto Rico, Antigua and Barbuda, Barbados, Montserrat, St. Kitts and Nevis, Anguilla and St. Maarten, Grenada, St. Vincent and the Grenadines.

Water-logged Texas dealt with the remnants of Tropical Storm Erin, which dropped up to 7 inches of rain in parts of San Antonio and Houston. Officials throughout central and southern Texas braced for the possibility of 10 to 15 inches of rain by Friday morning.

At least two people died Thursday in Erin's thunderstorms.

Shell Oil Co. evacuated 188 people this week from offshore facilities in Erin's path and said Thursday it was already monitoring Dean.

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Associated Press writers Guy Ellis in Castries, St. Lucia, David McFadden in Roseau, Dominica and Maura Axelrod in Fort-de-France, Martinique contributed to this report.

Here is the 11 a.m. advisory from the National Weather Service

Dean moving away from Lesser Antilles and strengthening...

A hurricane warning remains in effect for Martinique, Dominica and Guadeloupe and its dependencies.  The warning will likely be discontinued later today.

A tropical storm warning remains in effect for the U.S. Virgin Islands and Puerto Rico.  A tropical storm warning also remains in effect for the following islands of the Lesser Antilles; Saba, St. Eustatius, Montserrat, Antigua, Nevis, St Kitts, Barbuda, St. Maarten and Anguilla and the British Virgin Islands.

At 11 a.m. the hurricane warning for St. Lucia has been downgraded to a tropical storm warning.

At 11 a.m. the government of the Dominican Republic has changed the tropical storm watch to a tropical storm warning along the south coast from Cabo Engano to the Haiti/Dominican Republic border.  A hurricane watch has been issued from Cabo Beata to the Haiti/Dominican republic border.

At 11 a.m. tropical storm warning and a hurricane watch has been issued for Haiti from the Haiti/Dominican Republic border to Port-au-Prince.

A hurricane watch means that hurricane conditions are possible within the watch area...generally within 36 hours.

At 11 a.m. the tropical storm warning for Frenada and its dependencies has been discontinued.

Interests elsewhere in the Central and Western Caribbean, including Jamaica and the Cayman Islands, should closely monitor the progress of Dean.

For storm information specific to your area, please monitor products issued by your local weather office.

At 11 a.m. the eye of Hurricane Dean was located near latitude 14.6 north, longitude 62.6 west or about 105 miles west of Martinique and about 350 miles southeast of San Juan, Puerto Rico.

Dean is moving toward the west near 21 mph and this motion is expected to continue during the next 24 hours. This track will keep Dean over the Eastern Caribbean Sea today.

Maximum sustained winds have increased to near 105 mph with higher gusts.  Dean is a category two hurricane on the Saffir-Simpson scale.  Some strengthening is forecast during the next 24 hours and Dean is forecast to become a major hurricane.

Hurricane force winds extend outward up to 25 miles from the center and tropical storm force winds extend outward up to 185 miles.

Latest minimum central pressure recently reported by an Air Force hurricane hunter aircraft was 964 mb, 28.47 inches.

Storm total amounts of 1 to 2 inches can be expected from Dean over Puerto Rico and the Dominican Republic with maximum amounts up to 5 inches.  Additional rainfall accumulations of 1 to 2 inches are expected in the Lesser Antilles with isolated maximum amounts of 10 inches in mountainous areas.  These rains could cause life-threatening flash floods and mudslides.