Thunderstorms covered the Dominican Republic. Rivers burst their banks in dangerously deforested southern Haiti, where gusts uprooted a palm tree and flung it into a mud hut, injuring two people who were hospitalized in southern Les Cayes town.
Dennis grew to a Category 2 hurricane Thursday morning, becoming the third storm to threaten petroleum output in the Gulf of Mexico. Private forecaster AccuWeather put the storm right into U.S. oil and gas producing facilities.
Oil futures rose sharply Wednesday on concerns about Dennis but were down nearly $2 Thursday morning at $59.35 a barrel, as a series of terrorist blasts in London led investors to abandon riskier investments.
The hurricane follows Tropical Storm Cindy, which made landfall late Tuesday in Louisiana and hindered oil production and refining. On Thursday, remnants of Cindy hit parts of the Carolinas, prompting flash flood and tornado watches.
The Cayman Islands were on hurricane watch, and the southern Florida peninsula was on tropical storm watch, expecting severe conditions within 36 hours. Forecasters at the U.S. Hurricane Center in Miami said the storm could strike the United States on Sunday or Monday.
"It is possible that Dennis may become a major hurricane," the center warned.
Lead forecaster Martin Nelson said it was the first time the Atlantic hurricane season had four named storms this early since record-keeping began in 1851. The season runs from June 1 to Nov. 30.
By Thursday morning, Dennis's sustained wind reached nearly 105 mph with higher gusts, the U.S. National Weather Service said. The storm, the first hurricane of the Atlantic season, could dump 20 inches of rain over mountains in its path, including Jamaica's coffee-producing Blue Mountains, forecasters said.
Tropical storm force winds from Dennis's outer bands had already reached eastern Jamaica. "Regardless of landfall, Jamaica will have impacts ... practically all day and into the evening hours," warned forecaster Dave Roberts of the U.S. National Hurricane Center in Miami.
Last year, hurricanes Frances, Ivan and Jeanne tore through the Caribbean with a collective ferocity not seen in many years, causing hundreds of deaths and billions of dollars in damages.
Inside the U.S. base at Guantanamo Bay, where some 520 terror suspects are detained, the military prepared audio tapes in at least eight languages warning that a storm was coming and heavy steel shutters would be closed on some cell windows, Col. Mike Bumgarner said. He said the military had a contingency plan to move the prisoners if necessary.
Military officials had no immediate plans to evacuate troops or detainees at Camp Delta, which is about 150 yards from the ocean but was built to withstand winds up to 90 mph, according to Navy Cmdr. Anne Reese, supervisor of camp maintenance and construction.
At 11 a.m., the storm was centered 80 miles east of Kingston, Jamaica's capital, moving toward the northwest at 13 mph, the Hurricane Center said. Hurricane force winds extended up to 45 miles from the center and tropical storm force winds another 140 miles.
Radio stations in Haiti and Jamaica warned people to stay away from rivers that could overflow their banks.
"Particularly in the morning, the conditions will begin to deteriorate," Navy Lt. Dave Roberts, a meteorologist at the National Hurricane Center, told CBS Radio News. "The tropical storm-force winds in the next few hours should begin to reach the eastern extremes of Jamaica."
In southern Les Cayes, Jose Luis Paez, assistant chief of operations for U.N. civilian police, said 600 civilian police were trying to evacuate people from low-lying areas, but some refused to leave.
Jasmine Romelus, a 22-year-old student, was among them. "Hurricane?" she asked. "They always say there's going to be a hurricane and it never comes."
Hundreds of farmers and fishermen in the eastern Jamaica parish of St. Thomas also were cut off by flood waters. Emergency officials urged coastal residents — a large percentage of the population of 2.6 million — to move inland and ordered schools closed until Friday so they could be used as shelters. Airports at Kingston and Montego Bay were closed, and Air Jamaica canceled all flights.
Jamaica's Prime Minister P.J. Patterson abandoned the final day of the annual Caribbean summit in St. Lucia, to rush home. Before leaving, he called on Jamaicans to prepare "to protect those who are infirm, the elderly and the young."