Tropical Storm Isaac was near hurricane force as it bore down on the U.S. Gulf Coast on Tuesday and was expected to make landfall in the New Orleans area seven years after it was devastated by Hurricane Katrina.
Isaac's swirling winds and rain could pose a major test of New Orleans' new flood control systems and reinforced levees. Forecasts from the U.S. National Hurricane Centre showed the storm barrelling ashore late on Tuesday or early Wednesday near south-eastern Louisiana.
Energy companies evacuated offshore oil rigs and shut down U.S. Gulf Coast refineries as the storm threatened to batter the oil refining belt. As markets mulled Isaac's potential to tighten fuel supplies, prices for international benchmark Brent crude were up 28 cents to $112.55 (71 pounds) a barrel in early Tuesday activity.
"Isaac is likely to become a hurricane later today," the hurricane Centre said in its 5 a.m. EDT (10:00 a.m. British time) advisory. "Additional strengthening is forecast until the Centre moves inland."
Rain and tropical storm force winds were expected to spread into the region in the coming hours, bringing the threat of storm surge and flooding.
Isaac was centred 125 miles (205 km) southeast of the mouth of the Mississippi River with top sustained winds of 70 miles per hour (110 kph) - a speed that places the storm very near hurricane status - and swirling northwest at 12 mph (19 kph).
The storm was more than 400 miles (645 km) wide. Craig Fugate, director of the Federal Emergency Management Agency, said the worst effects may well be in Mississippi and Alabama. Isaac had New Orleans in its sights as the city still struggles to recover from Hurricane Katrina, which swept across it on August 29, 2005, killing more than 1,800 people and causing billions of dollars of damage.
Authorities urged thousands of residents in low-lying areas to evacuate, warning the storm could flood towns and cities in at least three U.S. Gulf Coast states with a storm surge of up to 12 feet (3.6 meters).
Isaac also threatened heavy rainfall, with possibly as much as 20 inches (50 cm) in areas, potentially triggering flooding in both inland and coastal areas.
"Inland flooding historically has been responsible for a lot of fatalities in tropical storms and hurricanes coming ashore," Hurricane Centre director Rick Knabb told CNN. "It's not just going to be a coastal event."
Residents in coastal communities from Louisiana to Mississippi stocked up on food and water and tried to secure their homes, cars and boats.
In New Orleans, a bumper-to-bumper stream of vehicles left the city on a highway toward Baton Rouge as people fled to higher ground. Others prepared, or were forced, to ride the storm out.
The storm was forecast to strengthen into a Category 1 hurricane, the lowest on the Saffir-Simpson scale, with top winds of 85 miles per hour (137 kph). While that would be well below the intensity of Katrina, which was a Category 3 storm, the size of Isaac's slow-moving system has forecasters predicting widespread flooding.
Along Canal Street in New Orleans' historic French Quarter, crews were boarding up the windows of stores and businesses.
'RIDING IT OUT'
"I'm not all that concerned about the storm. It's still a Category 1," said Charles Neeley, a 69-year-old contractor overseeing workers covering the windows of a CVS drugstore. "We usually ride out ones and twos and get the hell out for threes and fours."
Nonetheless, Neeley said he had stocked up on food and water at home and fuel for his generator.
"Our flights were cancelled so we're going to be here," said Karen Foley, a 23-year-old tourist who had planned to travel home to New Jersey with a friend. "We are just hoping the city doesn't get hit again. It doesn't deserve it."
Isaac killed at least 22 people and caused significant flooding and damage in Haiti and the Dominican Republic before skirting the southern tip of Florida on Sunday.
After Katrina, the U.S. Army Corps of Engineers built a $14.5 billion defence flood system of walls, floodgates, levees and pumps designed to protect the city against a massive tidal surge like the one that swamped New Orleans in Katrina's wake.
In low-lying Plaquemines Parish, which could be the first to be lashed by Isaac's winds and storm surge, workers scrambled to stack sandbags and reinforce levees as Isaac lurked in the Gulf.
Much of the parish lies outside the greater New Orleans levee system, and construction projects to bolster protection are not yet complete.
"We're really worried about the storm surge. We really need a few more years before we see an event like this," said Plaquemines Parish President Billy Nungesser.
As a precaution, as of Monday afternoon, the energy industry had shut down 78 percent of U.S. Gulf of Mexico crude production and 48 percent of its natural gas production, government figures showed.
The U.S. offshore oil patch produces about 23 percent of the country's oil output and 7 percent of its natural gas.
Once ashore, the storm could wreak havoc on low-lying fuel refineries along the Gulf Coast that account for about 40 percent of U.S. refining capacity.
Louisiana Governor Bobby Jindal said President Barack Obama approved his state's request for a federal disaster declaration, making federal funds available for disaster recovery activities like clearing debris.
The ports of Mobile, Alabama, and New Orleans were closed and barge traffic was suspended along southern portions of the Mississippi River.
(Additional reporting by Tom Brown, Sutton, David Adams and Kevin Gray in Miami, Ben Gruber and Kathy Finn in New Orleans, Emily Le Coz in Tupelo, Missisippi, Kristen Hays, Erwin Seba and Chris Baltimore in Houston and Verna Gates in Alabama; Writing by Kevin Gray; Editing by Tom Brown and Bill Trott)