This NOAA satellite image taken Tuesday, Aug. 21, 2012 shows Tropical Depression Nine currently spinning about 550 miles east of Guadeloupe, Mexico. Maximum sustained winds are up to 35 mph and the storm is expected to strengthen as it continues moving northwestward into the Caribbean Sea.ROSEAU, Dominica - Leaders across much of the Caribbean closed schools and government offices Wednesday as Tropical Storm Isaac churned toward the region, and the U.S. military postponed hearings for Sept. 11 prisoners ahead of a storm that could sweep across Cuba and perhaps eventually menace Florida as a hurricane.
The storm was 25 miles (40 kilometers) south-southeast of the French Caribbean island of Guadeloupe late Wednesday afternoon, with maximum sustained winds of 45 mph (75 kph). Isaac was moving west at 22 mph (35 kph) and was expected to become a hurricane by Thursday night or Friday, the U.S. National Hurricane Center said.
Dominica Prime Minister Roosevelt Skerrit urged people to stay home from work Wednesday.
"I want us all to be safe," he said. "I don't want lives to be lost."
Authorities in Puerto Rico reported that a 75-year-old woman died in the northern city of Bayamon when she fell from a second-floor balcony while filling a barrel with water in preparation for the storm.
Military authorities at the U.S. base in Guantanamo Bay, Cuba, canceled several days of pretrial hearings in the case of five prisoners charged in the Sept. 11 attacks. They also planned to evacuate about 200 people, including legal teams and relatives of Sept. 11 victims.
Isaac also posed a possible threat to Florida during next week's Republican National Convention in Tampa, according to forecasters, though the hurricane's track was uncertain.
Tess Hunneybell, owner of Manico River Eco Resort, which features luxury treehouses perched in the foothills of Dominica's Morne Aux Diables volcano, said there was still barely a breeze Wednesday afternoon as dark clouds gathered over the sea.
"Right now, it's definitely the calm before the storm. But we can see the clouds coming this way," Hunneybell said.
She and others wrapped the treehouses in tarpaulin and nailed shut louvre doors. There were no guests because flights to the jagged, densely forested island had been suspended.
In Puerto Rico, Gov. Luis Fortuno declared a state of emergency and activated the National Guard. He also canceled classes and closed government agencies. Federal officials also closed the popular San Felipe del Morro castle in Old San Juan. The storm was expected to pass just south of Puerto Rico on Thursday.
The U.S. Coast Guard closed all ports in Puerto Rico and the U.S. Virgin Islands to incoming commercial ships and warned that all commercial vessels bigger than 200 gross tons must leave or obtain permission to remain in port.
The U.S. Virgin Islands commissioner of public works, Darryl Smalls, said crews distributed sandbags to residents in St. Croix, where schools and government offices were ordered not to open Thursday. St. Kitts announced similar closures for Wednesday.
As he campaigned in Nevada, President Barack Obama received an update from the Federal Emergency Management Agencyy on U.S. preparations for Isaac, deputy press secretary Josh Earnest reported.
"FEMA has been in close coordination with local officials and emergency managers in Puerto Rico and the U.S. Virgin Islands," Earnest told reporters as Obama flew to a later stop in New York. Earnest said FEMA had deployed teams to both locations.
The storm was unleashing heavy rain in Guadeloupe on Wednesday afternoon that was expected to worsen, said local chief meteorologist Norbert Aouizerats. He said wind gusts could top 62 mph (100 kph).
In Martinique, officials warned of swollen rivers and flooding. Meteorologist Jean-Noel Degrace said at least 3 inches (8 centimeters) of rain had fallen Wednesday morning. The leader of Martinique, Laurent Prevost, urged people in low-lying areas to evacuate.
In the Dominican Republic, authorities banned boats from entering its waters and warned of heavy rains from Thursday through Saturday.
Liat airline and American Eagle canceled flights to islands including Dominica, the U.S. Virgin Islands, Guadeloupe and Martinique.
The storm's center was expected to move over the Leeward Islands on Wednesday evening, and forecasters said it was likely to hit the Dominican Republic and Haiti as a hurricane Friday. It was predicted to move on to Cuba as a tropical storm.
On the island of Vieques, which lies just east of Puerto Rico, people prepared for the government to temporarily shut off power.
Glenn Curry, an owner of Bananas Guesthouse, said he closed the restaurant and would move guests to a higher floor.
"I don't think this is going to be a major storm, but it's going to be noisy and unpleasant for a few hours," he said.
The general manager of the Hilton Golf & Casino Resort in the southern city of Ponce, Puerto Rico's second largest city, said he had warned guests about the impending storm.
"We expect bad weather, rain, wind, but nothing to the extent of danger," said Gunther Mainka.
He said the hotel prepares for storms in July, including trimming the numerous palm trees that surround the resort.
"They get a big haircut," he said. "All the loose branches go down, all the coconuts go down."