As Category 5 Hurricane Irma churns through the Caribbean and Hurricane Jose strengthens, The U.S. National Hurricane Center (NHC) issued hurricane and storm surge watches for parts of southern Florida in a public advisory on Thursday. A "storm surge watch," meaning there could be life-threatening inundation from rising floods and waves in the next 48 hours, is in effect for the Jupiter Inlet to Bonita Beach and the Florida Keys, the NHC said. A storm surge at high tide could bring water levels between five and 10 feet above ground in the areas under watch. The NHC put a hurricane watch in effect for the Jupiter Inlet southward around the Florida peninsula to Bonita Beach, the Florida Keys, Lake Okeechobee and Florida Bay. Source: U.S. National Hurricane Center "Based on what we know now, Florida will have major hurricane impacts with deadly storm surge and life-threatening winds, and we can expect this all on the east coast," Florida Gov. Rick Scott said in a news conference on Thursday, while stressing that all Floridians should be prepared to evacuate. "Possessions can be replaced," Scott said. "Your family cannot." The Center also announced that the "extremely dangerous Hurricane Irma" is "very near the Turks and Caicos Islands and heading for the Bahamas." Hurricane Irma killed at least four people on the Caribbean island of St. Martin, French Prime Minister Edouard Philippe said. The storm left the island of Barbuda devastated, killing at least one person, and now has set its sights on Florida. Television footage of the Franco-Dutch island of St. Martin showed a damaged marina with boats tossed into piles, submerged streets and flooded homes. Power was knocked out on St. Martin, St. Barthelemy and in parts of the U.S. territory of Puerto Rico. "It is an enormous disaster, 95 percent of the island is destroyed. I am in shock," Daniel Gibbs, chairman of a local council on St. Martin, told Radio Caribbean International.

French Interior Minister Gerard Collomb said at least eight people were killed in the country's Caribbean territories and that the toll was likely to rise. "We did not have the time yet to explore all the shores," Collomb told Franceinfo radio, adding that 23 people were also injured. In all, at least 10 people were reported killed by Irma on four islands. Irma caused "enormous damage" to the Dutch side of St. Martin, called Sint Maarten, the Dutch Royal Navy said. The navy tweeted images gathered by helicopter of damaged houses, hotels and boats. The airport was unreachable, it said. The hurricane, with top sustained winds of 175 miles per hour, was on track to reach Florida on Saturday or Sunday, becoming the second major hurricane to hit the U.S. mainland in as many weeks after Hurricane Harvey.

The eye of Irma was moving west-northwest near 16 mph, meaning it would continue to move between Hispaniola and the Turks and Caicos Islands on Thursday evening, the NHC said. The island of Barbuda is a scene of "total carnage" and the tiny two-island nation will seek international assistance, said Gaston Browne, prime minister of Antigua and Barbuda. Browne told the BBC about half of Barbuda's population of some 1,800 were homeless while nine out of 10 buildings had suffered some damage and many were destroyed.

Rain and wind

"We flew into Barbuda only to see total carnage. It was easily one of the most emotionally painful experiences that I have had," Browne said in an interview on BBC Radio Four. "Approximately 50 percent of them (residents of Barbuda) are literally homeless at this time. They are bunking together, we are trying to get ... relief supplies to them first thing tomorrow morning," he said, adding that it would take months or years to restore some level of normalcy to the island. Browne said one person was killed on Barbuda. A surfer was also reported killed on Barbados.

Irma hit Puerto Rico early on Thursday, buffeting its capital San Juan with rain and wind that scattered tree limbs across roadways. At least half of Puerto Rico's homes and businesses were without power, according to Twitter posts and a message posted by an island utility executive. The NHC said it was the strongest hurricane ever recorded in the Atlantic Ocean and one of the five most forceful storms to hit the Atlantic basin in 82 years. Irma's precise course remained uncertain but it was likely to be downgraded to a Category 4 storm by the time it makes landfall in Florida, the NHC said. It has become a little less organized over the past few hours but the threat of direct hurricane impacts in Florida over the weekend and early next week were increasing, it said. Hurricane watches were in effect for the northwestern Bahamas and the Turks and Caicos islands, where storm surge is expected to raise water levels 15 to 20 feet above normal tide levels.

Storm preparations

Two other hurricanes formed on Wednesday. Jose, another Atlantic hurricane moving in Irma's direction, was upgraded to a Category 3 storm by the NHC in a 5 p.m. ET advisory. The hurricane, now sustaining winds of 120 mph, is moving west-northwest about 590 miles off the coast of the Caribbean Lesser Antilles islands. The other hurricane, Katia, is located in the Gulf of Mexico and poses no threat to the United States, according to U.S. forecasters. Katia is expected to begin moving toward the coast of Mexico and strengthen Thursday or early Friday, the NHC said in a 5 p.m. ET advisory. The storm activity comes after Harvey claimed about 60 lives and caused property damage estimated as high as $180 billion in Texas and Louisiana. Florida emergency management officials began evacuations in advance of Irma's arrival, ordering tourists to leave the Florida Keys. Evacuation of residents from the Keys began Wednesday evening. A growing number of counties in Florida are following suit, issuing evacuation orders in hopes of moving vulnerable populations before Irma makes it impossible to flee or receive help. Monroe County and Miami-Dade County, two of the southernmost regions of the state, have made evacuations mandatory. Broward County and Collier County have issued voluntary evacuation orders. Georgia Gov. Nathan Deal issued a mandatory evacuation order on Thursday for the southeast coast of his state, in addition to declaring a state of emergency in 30 counties and mobilizing 5,000 Georgia National Guard members for active duty in the response and recovery to the storm. More than 6,800 volunteers have signed up to respond to Hurricane Irma in the last 24 hours, Gov. Scott said at a Thursday news conference, far short of the 17,000 Scott says are needed in the state overall. "This storm has the potential to catastrophically devastate our state," Scott said.

Carnival, Royal Caribbean and Norwegian Cruise Lines have canceled all voyages scheduled to depart from Florida on Friday, alongside cancellations from Disney Cruise Lines and Bahamas Paradise Cruise Lines. Hospitality service Airbnb launched a "Disaster Response Program" for Florida and Georgia residents to offer free temporary housing to evacuees through the company's app. Irma is expected to turn northward after making contact with a trough on the eastern United States, but the timing and exact direction of the turn are unknown, as multiple weather models yield different potential paths for the storm. The unknown variables of where and when Irma will strike "is the most important question and one still filled with uncertainty," the NHC said. Ed Rappaport, the Miami-based NHC's acting director, told WFOR-TV that Irma was a "once-in-a-generation storm." Rashida tweet In Cuba, 90 miles south of the Keys, authorities posted a hurricane alert for the island's central and eastern regions, as residents in Havana, the capital, waited in lines to stock up on food, water and gasoline. Residents in most coastal communities of densely populated Miami-Dade County were ordered to move to higher ground beginning at 9 a.m. ET on Thursday, Mayor Carlos Gimenez said.

Trump resort in storm path

U.S. President Donald Trump said he and aides were monitoring Irma's progress. "But it looks like it could be something that will be not good. Believe me, not good," he told reporters. Trump, whose water-front Mar-a-Lago estate in Palm Beach, Florida, could take a direct hit from the storm, has already approved emergency declarations for Florida, Puerto Rico, and the U.S. Virgin Islands, mobilizing federal disaster relief efforts. He spoke with governors of all three by telephone on Wednesday, the White House said. Florida Governor Rick Scott said Irma could be more devastating than Hurricane Andrew, a Category 5 storm that struck the state in 1992 and still ranks as one of the costliest ever in the United States. Residents in most coastal communities of densely populated Miami-Dade County were ordered to move to higher ground beginning at 9 a.m. ET on Thursday, Mayor Carlos Gimenez announced on Wednesday. The evacuation orders will affect more than 100,000 residents, the Miami Herald reported. Gasoline stations around the state struggled to meet rising demand of motorists anxious to top off their tanks as Irma approached, with some locations running dry on Wednesday. Scott told a news conference in the Keys that 7,000 National Guard troops would report for duty on Friday, ahead of the storm's expected arrival. Statewide emergency declarations were issued in both North and South Carolina, and Georgia Governor Nathan Deal declared an emergency for six coastal counties in anticipation of Irma's arrival. — Reuters contributed to this report.

WATCH: Irma could hit Florida Sunday