US President George Bush described Hurricane Gustav as "very dangerous", and urged people in the storm zone to heed evacuation orders. Fleeing New Orleans residents crowded onto roads out of the city on Sunday.
A weakened Hurricane Gustav took aim at the United States Sunday, sweeping into the Gulf of Mexico from Cuba after a week-long rampage through the Caribbean that left at least 81 dead.
New Orleans mayor Ray Nagin, desperate to avoid a replay of the 2005 Katrina catastrophe, ordered the city emptied on Sunday in the face of what he called "the storm of the century" and roads out were jammed with fleeing residents.
In Cuba, Gustav tore off roofs, flattened buildings and plunged communities into darkness as it smashed through the Isle of Youth, which has more than 200,000 residents, then tore across mainland Cuba southwest of Havana, which has a population of more than two million.
It lost some of its punch in the process, with US officials downgrading it from four to three.
There were no reported deaths in Cuba, after the storm claimed lives in the Haiti, the Dominican Republic and Jamaica.
"Maximum sustained winds have decreased to near 125 miles (205 kilometers) per hour with higher gusts," the US National Hurricane Center said. "Gustav is a category three hurricane on the Saffir-Simpson scale."
But the center warned it could regain category four strength by the end of Sunday as it moved across warm waters of the Gulf.
"Gustav is forecast to remain a major hurricane until landfall," which was forceast for Monday, the center said.
At 0900 GMT, Gustav's eye was about 425 miles (680 kilometers) southeast of the mouth of the Mississippi River, the US National Hurricane Center said. It was moving northwest at 16 miles (26 kilometers) an hour.
Republican White House hopeful John McCain and his running-mate Sarah Palin said they would suspend their normal election campaign and visit to Mississippi to inspect preparations for Gustav's arrival.
Traffic clogged roadways out of New Orleans as residents fled a potentially disastrous strike on the city just three years after Katrina left some 1,800 dead along the coast.
Major oil producers BP, ConocoPhillips and Shell on Thursday evacuated workers from their facilities in the Gulf where nearly a quarter of US crude oil installations are located.
Cuban national television reported that the scene on the Isle of Youth was one of devastation after the monster storm ground its way across the low-lying island of fishing villages, factories and citrus farms.
"The situation is very difficult," acknowledged Ana Delgado, president of the Municipal Defense Council there. "The damage is widespread."
Homes were under water, warehouses toppled, and roads washed away on the Isle, state television said, adding there were some injuries though no immediate reports of deaths.
More than 250,000 were evacuated from western parts of mainland Cuba before the storm hit near the town of Carraguao, 100 kilometers (62 miles) southwest of Havana, then crossed into the Gulf of Mexico, the Cuban weather service said.
Used to fairly frequent smaller tropical storms, Havana residents ran around town Saturday gathering candles and food, boiling water and taping up windows. But the steady flow of updates on state television alarmed many.
"Really, I just did not expect this -- it has been a long time since we have been hit by such a powerful hurricane, and this Gustav looks like it will be quite strong," said retired actress Gliseria Farinas.
A key concern was for the crowded and charming colonial-era Old Havana, which UNESCO declared a World Heritage Site in 1982. Its fragile, centuries-old buildings are prone to cave-ins after heavy rains, though most of Cuba's housing stock is old and fragile.
Cuban authorities have said that in Havana alone there are 1,000 buildings in "critical condition". These include about 8,000 structures housing some 26,000 people, many of them in Old Havana.
Early Saturday, a Caymans official reported heavy damage from Gustav on Cayman Brac, the large eastern island in the group, with power and water supplies down. Hundreds of people fled into shelters on Grand and Little Cayman islands to escape flooding in some areas.
Earlier Gustav's path of destruction left 66 dead and 10 missing in Haiti. In neighboring Dominican Republic, the death toll stood at eight, while in Jamaica the toll stood at seven, with many thousands displaced.
Date created : 2008-08-31