Tropical Storm Isaac entered the eastern Caribbean Wednesday night and is expected to bring tropical storm conditions to Puerto Rico Thursday, the National Hurricane Center in Miami said.
As of 11 p.m., Isaac had maximum sustained winds of 45 miles per hour as it moved west at 20 mph about 270 miles southeast of San Juan, Puerto Rico.
Tropical storm conditions should subside over the Leeward Islands by Thursday morning, according to the National Hurricane Center. Isaac was expected to pass south of Puerto Rico and the Virgin Islands Thursday, and approach the Dominican Republican Thursday night and Friday.
Although South Florida is still days away from any potential threat, Hurricane Center Director Rick Knabb urged residents to prepare.
"We are within that five-day cone, and there is a potential for an impact starting in the latter half of the weekend," Knabb said. "There is a not a guarantee of a direct hit from this."
Florida Gov. Rick Scott issued a statement Wednesday afternoon, urging residents to monitor the storm.
“As Florida’s governor, I’m urging everyone across the state to monitor the storm track, and use the next several days to prepare for a potential storm," Scott said. "As we know, storms this far from land are still unpredictable and everyone should be vigilant and prepared."
The storm is expected to strengthen somewhat over the next 48 hours and could become a hurricane by Thursday night, which would make it the fourth hurricane of the 2012 season.
Hurricane and tropical storm watches and warnings were in effect for many islands in the Caribbean.
One has not been issued yet for Cuba, but as the storm approached, authorities at the U.S. base in Guantanamo Bay canceled several days of pretrial hearings in the case of five detainees charged in the Sept. 11 attacks. They planned to evacuate about 200 people, including legal teams and relatives of Sept. 11 victims.
A state of emergency was declared in Puerto Rico, where the National Guard was activated. A 75-year-old woman there died Wednesday in Bayamon when she fell from a second-floor balcony while filling a barrel with water as she prepared for the storm, authorities said.
Isaac was expected to pass just south of the island on Thursday.
"I would be at least preparing for the possibility of weather that makes it difficult to do any more preparations as soon as Sunday. If you really want to be ahead of the game, you want to be done by Saturday, in case it speeds up," Knabb said.
There are a lot of variables present before Isaac potentially moves towards the southeast United States. Possible land interactions, teamed with steering currents, could turn the system to the east or west of the peninsula.
Knabb said people have the luxury of time to review their preparations and buy what they need this week.
"Once we get into the weekend, that could be when we are in the warning, watch time frame," he said.
He added that it's human nature to become used to not having hurricanes because Wilma was the last one that impacted South Florida.
"We have to remind ourselves that at some point our luck is going to run out," Knabb said. "There are probably a lot of people who have never been through a hurricane. So, you can help out your friends who are less familiar with a hurricane threat," Knabb said.
Knabb also added it was uncertain if the storm would have any effect on the 2012 Republican National Convention in Tampa next week.
"Tampa is one of the many places that could be affected by Isaac down the road in the U.S.," Knabb said. "They might not see any impacts."
James Davis, the convention's director of communications, said they have been working closely with officials to monitor the storm.
“The convention is working closely with our partners at the federal, state and local levels to monitor the weather – and we have contingency plans in place to ensure the health and safety of convention delegates, guests and visitors, and the Tampa Bay community. We are looking forward to a great convention,” Davis said in an email statement.
Scott said convention organizers have planned for an event such as a hurricane.
"Florida’s state emergency management team and local emergency teams have been working closely with convention officials and have been planning for this event for more than a year, and the possibility of a hurricane hitting the convention has been part of that planning process," Scott said.
Tampa Mayor Bob Buckhorn told CNN on Wednesday morning that if the storm hit as a catastrophic hurricane he could pull the plug on the convention.
"Well, absolutely, we're prepared to call it off," Buckhorn said on the network's Early Start with John Berman. "Safety and human life trump politics. I think the RNC recognizes that. The organizers, certainly Gov. (Mitt) Romney, recognize that."
Tropical storm force winds extended outward for up to 140 miles from the center of Isaac Wednesday night.
A hurricane watch was in effect for Vieques, Culebra and Haiti. That means that hurricane conditions are possible in the area. A watch is usually issued 48 hours before the first tropical storm force winds are expected to arrive.
A hurricane warning was in effect for the south coast of the Dominican Republic from Isla Saona westward to the Haiti-Dominican Republic southern border.
A tropical storm watch was in effect for the southeastern Bahamas and for the Turks and Caicos Islands.
A tropical storm warning was in effect for Dominica, St. Kitts, Nevis, Antigua, Barbuda, Montserrat, Anguilla, Saba, St. Eustatius, St. Maarten, the British Virgin Islands, Puerto Rico, Vieques, Culebra and the U.S. Virgin Islands, and the north coast of the Dominican Republic from the country's northern border with Haiti eastward to north of Isla Saona.
Meanwhile, Tropical Depression 10 formed Wednesday morning out in the eastern Atlantic. It had maximum sustained winds of 35 mph as of 11 p.m. The depression could become a tropical storm Thursday.