KINGSTON, Jamaica -- Gathering strength over the central Caribbean, Tropical Storm Ernesto steamed toward Jamaica Saturday and threatened to enter the Gulf of Mexico within days as the first hurricane of the 2006 Atlantic season.

Ernesto, packing 60 mph winds, could be near hurricane strength by Sunday. Still, it was too soon to predict whether it would hit the United States, said Michael Brennan, a meteorologist with the National Hurricane Center in Miami.

"People should pay attention, especially people on the Gulf coast," Brennan said. "We're in the middle of hurricane season and it's a good time for people to update their hurricane plans."

Jamaica and the Cayman Islands, which both stood in the storm's path, issued hurricane watches, meaning severe conditions including winds of at least 74 mph were possible over the next 48 hours. Cuba also issued a hurricane watch for provinces in the country's southeast.

Tropical storm warnings also were in effect for Jamaica and Haiti's southern coast. The hurricane center advised people in Mexico, the southeastern Gulf of Mexico and the Florida Keys to monitor the storm.

In Washington, top Homeland Security Department and Federal Emergency Management Agency officials gathered for the first of a series of videoconference briefings to put responders on high alert for Ernesto. One document released at the briefing forecast Ernesto upgrading by Thursday morning to a Category 3 storm, the same as Hurricane Katrina at landfall last year, and heading toward New Orleans.

Homeland Security spokesman Russ Knocke noted the weather projections would almost certainly change over the course of the next several days, and that Ernesto's size and potential landfall could not yet be accurately predicted. Still, he said, Ernesto "has the makings of becoming the first major storm of the season."

"It's being taken very seriously," Knocke said.

Ernesto was on a course that would bring it over Jamaica by Sunday afternoon, dumping 4 to 8 inches of rain on the island with up to a foot possible in some areas, the hurricane center said. Fisherman were warned to return to shore - with tides of up to 3 feet above normal expected - and Prime Minister Portia Simpson Miller met with disaster agencies to prepare.

Jamaica issued advisories by radio and television for residents in low-lying areas across the island to be prepared to evacuate if necessary. Ernesto was expected to strengthen within the next 24 hours and could be near hurricane strength as it nears Jamaica and western Haiti on Sunday, the hurricane center said.

"We are concerned about the flood risk to parishes that were affected in the past, so that is the major concern right now," said Nadine Newsome, a spokeswoman for the Office of Disaster Preparedness and Emergency Management.

At 5 p.m. Saturday, Ernesto had maximum sustained winds near 60 mph with higher gusts. The fifth named storm of the Atlantic hurricane season was centered 190 miles south-southeast of Port-au-Prince, Haiti, and 375 miles east-southeast of Kingston, Jamaica.

The storm was moving west-northwest near 13 mph. It was expected to bring 4 to 8 inches of rain to Haiti and the Dominican Republic, which share the island of Hispaniola, with up to a foot possible in some areas, the hurricane center said. Tides of up to 3 feet above normal were expected in Haiti.

As heavy showers hit Kingston on Saturday afternoon, traffic jams formed with motorists trying to reach stores. People waited in long lines at supermarkets, filling grocery cars with canned goods, batteries and candles.

"It's nature and we can't stop it from taking its course," said taxi driver Patrick Wallace, 55. "I'm hoping if it hits, it will be in the morning so we can see what's going on."

Despite sunny skies in the British territory of the Caymans, people flooded gas stations, hardware stores and supermarkets, as well as formed big lines to withdraw money from cash machines. Businesses also boarded up.

Damien Dilbert, owner of Big Daddy's liquor store on Seven Mile Beach just outside the capital, said the store has been "crazy busy."

"Every time there is always a hurricane, people have their hurricane parties and buy up the liquor," he said.

Tourists appeared to take word of the impending weather in stride.

Debbie Curigliano, of Bridgeville, Pa., said she and her husband would be relaxing and drinking during the storm. They were staying at a resort in Seven Mile Beach.

"I am going to put all my faith in the hotel and I am sure they will guide me right through it," she said.

In Haiti, emergency officials went on local radio to warn people living in flimsy shantytowns on the southern coast to seek shelter in schools and churches.

"These people could be in great danger," said Adel Nazaire, a coordinator with Haiti's civil protection agency. "Flooding is the biggest concern because a lot of residents live along the rivers and the sea."

Elisabeth Verluyten, a disaster management official with the Pan-American Health Organization in Port-au-Prince, said raising awareness is vital as many people won't leave their homes "because they're afraid of losing the little they have."

The impoverished Caribbean nation is 90 percent deforested, increasing vulnerability to deadly flooding and mudslides.

Fears that the storm could damage offshore energy facilities in the Gulf of Mexico sent oil and natural-gas prices higher. Oil producers operating in the Gulf said they were prepared to evacuate nonessential personnel if needed.

Meanwhile, former Tropical Storm Debby, now a depression with maximum winds of 30 mph, was expected to stay over the open Atlantic, posing only a threat to ships. At 5 p.m., the center of the storm was about 1,410 miles west-southwest of the Azores.

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