The governor of Puerto Rico has declared a preemptive state of emergency and activated the territory's National Guard ahead of Hurricane Irma, a Category 3 storm that is expected to strengthen further before making possible landfall on the island by mid-week.
Forecasters say the dangerous storm also looks increasingly likely to hit the U.S. East Coast, either in South Florida or the Carolinas.
"We have established protocols for the safety of all," Puerto Rico Gov. Ricardo Rossello said, urging islanders to take precautions.
Rossello said 4 to 8 inches of rain were expected, with wind gusts up to 60 mph.
Brian McNoldy, a senior research associate at the University of Miami's Rosenthiel School of Marine and Atmospheric Sciences, writes in a blog post that the latest tracks for Irma are "bad news for a lot of places from the Leeward islands, Puerto Rico, Dominican Republic, Haiti, Cuba, the Bahamas, and then the U.S."
Although it's still too early to say whether Irma would make landfall on the mainland U.S., McNoldy cites long-range forecasts showing possible landfalls on the border between the Carolinas, or alternately near Miami.
The National Hurricane Center in Miami has issued a hurricane watch for Puerto Rico and the Virgin Islands and a hurricane warning for the Leeward Islands north of Guadeloupe, including Antigua and Barbuda, Anguilla, Montserrat, St. Kitts and Nevis, St. Martin/St. Maarten, Saba, St. Eustatius and St. Barthelemy. A watch was also in effect for Guadeloupe as well as Vieques and Culebra.
The current forecast track has the storm passing closest to St. Martin and Anguilla, where it is expected to hit with 100 mph winds and heavy rain on Tuesday before moving westward toward Puerto Rico on Wednesday.
The Associated Press writes that: "Antigua's prime minister, Gaston Browne, urged people to take preventative measures in case the storm should keep on its current arc, saying that should include cleaning drains and removing objects that could be sent flying by high winds. Workers began pruning trees and shrubs to reduce chances for branches to tear down power and phone lines.
"The passage of a hurricane is not a matter to be taken lightly, but we must not panic," Browne said in a statement.
In the Dominican Republic, Public Works Minister Gonzalo Castillo was quoted by the AP as saying workers were clearing away road works and blocked sewer drains in preparation for the storm.
Earlier, some models had the storm re-curving away from the U.S. coast, but McNoldy writes: "At this point, Florida is definitely at risk from at least a close encounter if not a direct landfall from a major hurricane. The southeast U.S. coast is also still at an elevated risk of significant impacts."