Irene grew into a Category 2 hurricane late yesterday and the U.S. National Hurricane Center in Miami said it could reach Category 3 today and possibly become a monster Category 4 storm within 72 hours.
'We didn't anticipate it gaining this much strength this early,' said center meteorologist Chris Landsea, adding that the ocean's warm temperatures and the current atmosphere is 'very conducive' to energising storms.
Forecasters said it could still be that strong when it slams into the U.S., possibly landing in Florida, Georgia, or South Carolina. Irene is expected to rake the Turks and Caicos and the Bahamas today and tomorrow.
© Getty ImagesPanic buying: Residents in West Palm Beach, Florida, are preparing for the arrival of Hurricane Irene as it sweeps through the Caribbean
© EPAStorm damage: The beach at Los Gringos de Nagua in the Dominican Republic has been affected by the passing of hurricane Irene
© ReutersCleaning up: A man tries to push the floodwaters away from outside his home in Loiza, Puerto Rico
© CNNPath: The current projected track for the hurricane has it moving up the eastern side of Florida
National Hurricane Centre spokesman Dennis Feltgen urged south Florida residents to monitor the storm carefully, to double check their supplies of food and fuel and to review their hurricane plans.
'We must prepare for the worst and hope for the best,' said Joe Martinez, chairman of the Miami-Dade County Commission.
Officials in Charleston, South Carolina, also warned residents to monitor Irene closely. It has been six years since a hurricane hit the South Carolina coast, said Joe Farmer of the state Emergency Management Division.
Earlier, the storm slashed directly across Puerto Rico, tearing up trees and knocking out power to more than a million people, then headed out to sea north of the Dominican Republic, where the powerful hurricane's outer bands were buffeting the north coast with dangerous sea surge and downpours.
© AFP/ Getty ImagesWaiting and hoping: A worried woman watches from a beach in Santo Domingo in the Dominican as the country braces for the imminent impact of Hurricane Irene
© EPAEvacuation: People living near the seashore in the Dominican Republic have been moved out of their houses
© CNNSwirl of destructive colour: The current satellite image of the hurricane shows its powerful mass
Others hunkered down inside their homes as the winds howled outside and heavy waves pounded the piers and washed onto coastal boulevards.
Forecasters say because of its track, the mountains of Hispaniola will probably do little to weaken the storm that is projected to hit the U.S. mainland on Thursday or Friday.
Irene is the first hurricane of the Atlantic storm season.
The heavily-populated south east Florida coast is in the direct line of numerous forecast cones.
However, the NHC stressed Irene's path still remains uncertain and it could make landfall anywhere from the Florida Keys to the Carolinas.
© EPAWet and wild: Steady high winds of up to 130kmph with even more powerful gusts are moving across Nagua in the Dominican Republic
© Associated PressGetting closer: This satellite image taken at 2am today shows Hurricane Irene as it spins north of Hispaniola, moving ever nearer to the U.S.
Kristina Pydynowski, a meteorologist with State College, Pennsylvania-based AccuWeather Inc., said it could become a Category 3 hurricane with sustained winds of at least 111 mph.
She said: 'We definitely think it'll make landfall in the south-eastern part of the U.S.'
The NHC says a storm of this magnitude would cause 'devastating damage' with a 'high risk of injury or death.'
Puerto Rico took a pounding yesterday morning with at least five rivers bursting their banks.
© Associated PressWeather forecast for Wednesday: Experts predict Irene will move up the east coast of Florida on Thursday, producing rain from Missouri through the Ohio Valley
The fast-changing storm has downed trees and caused widespread power cuts in the U.S. Virgin Islands as it shifted north over Caribbean territory.
It is feared the hurricane could cause dangerous mudslides and floods in Dominican Republic, the NHC said.
Dominican officials said the government had emergency food available for 1.5million people if needed and the country's military and public safety brigades were on alert.
'We have taken all precautions,' presidential spokesman Rafael Nunez said.
© Associated PressPreparations: Florida resident Jay Coleman fills up spare petrol containers as he anticipates the disruption caused by Irene
© Associated PressQueuing up: Florida resident Justin Gomez is at the front of the queue to stockpile fuel as the traffic lines up behind him
© CNNGuessing game: The various projected paths of the hurricane show that it could pass very close to the Florida coast, or move a little further out to sea
Residents of Antigua reported rains, strong squalls and surf as the storm passed the Leeward Islands in the north-east corner of the Caribbean.
Hurricane watches and warnings were in effect in the U.S. Virgin Islands, Puerto Rico and the Dominican Republic.
Tropical storm warnings were in effect for most of the north-eastern Caribbean islands, and for Haiti.
In San Juan, dozens of people sought emergency shelter ahead of Irene, which is expected to dump up to 10in (25cm) of rain in Puerto Rico.
© EPABraving the elements: A lady walks along the debris-strewn beach at Los Gringos de Nagua, where storm warnings are at their maximum
She said: 'You can hear the wind, the gusts are relentless, she said. I can't see anything because I've closed everything.'
Puerto Rico's main airport was swamped with people on Sunday, the usual crowds combined with people rushing to get off the island before the storm or stranded because flights to a number of other islands had been cancelled. There were long lines at check-in counters and at the airport hotel.
Strong winds and rain were battering the outlying Puerto Rican islands of Culebra and Vieques, where 150 tourists were evacuated, according to Governor Luis Fortuno.
At least 120,000 people were without power and another 13,000 without water as the storm approached.
© AFP/ Getty ImagesMoving north: A satellite image from the National Oceanic and Atmospheric Administration (NOAA) shows Hurricane Irene over Puerto Rico and moving towards the Dominican and Haiti
The U.S. hurricane centre said the main impediment to the storm's progress over the next couple of days will be interaction with land.
If Irene passes over Hispaniola's mountains or over parts of eastern Cuba, the storm could weaken more than currently expected.
In the U.S. Virgin Islands, Governor John deJongh declared a state of emergency in order to impose storm curfews.
Governors spokesman Jean Greaux said: 'We've got what appears to be a direct hit on St Croix.'
Residents of Cuba, the Turks and Caicos Islands, the Bahamas and the south-eastern United States were urged to monitor Irene's progress as the storm headed their way.
© ReutersFlooded: A crop plantation is submerged by water after Hurricane Irene hit the municipality of Loiza, in Puerto Rico
Depending on its eventual path and possible turns, Irene might still pose a threat to U.S. oil and gas installations in the Gulf of Mexico, but forecasters say it is too early to predict with certitude.
An early northward turn would bring it near the Georgia-South Carolina coast late in the week. But a later turn could keep it over the warm Caribbean waters until it reached the Gulf of Mexico, which could make it a much more powerful hurricane.
Tropical Storm Harvey, which hit the coast of Belize in Central America on Saturday, weakened earlier on Sunday to a tropical depression.
But the hurricane center said it was still producing heavy rains over Guatemala and south-eastern Mexico. It was expected to dissipate by Monday.
Mudslides and flooding could affect agricultural output in Central America, but this year's coffee and sugar harvests are largely complete.
Taking a look at this soon to be category 4 as I am here in Fayetteville, NC. Uhhh, is that tracking putting it right over me on Sunday Morning? I was in an Eco Resort made with 2x4's during Hurricane Hugo and Hurricane Marilyn in The Virgin Islands. The aftermath was like a bomb had just gone off. It was an eerie feeling. However, a hurricane is like a deep cleansing bath, soaking the land and breaking up debris. If we all did not have so much junk then the mess would seem less devastating.