New Orleans - Tropical Storm Isaac bore down on the US Gulf Coast on Tuesday, packing swirling winds and rain and posing a major test of the region's new flood control systems seven years after Hurricane Katrina sent walls of water crashing across its shoreline.
Rain and tropical storm force winds were expected to spread into the region in the coming hours, the US National Hurricane Center said, as computer forecast models increasingly showed the storm likely to make landfall late on Tuesday near southeastern Louisiana as a full-blown hurricane.
Isaac appeared to be taking direct aim at New Orleans, which would be a cruel blow for a city still struggling to recover from Hurricane Katrina which swept across the city almost exactly 7 years ago on August 29, 2005, killing more than 1 800 people and causing billions of dollars of damage.
Authorities encouraged thousands of residents in low-lying areas to evacuate, warning the storm could flood towns and cities in at least three US Gulf Coast states with a storm surge of up to 3.6 metres.
Isaac also threatened heavy rainfall, with possibly as much as 46cm in areas, potentially triggering flooding in some coastal areas.
The storm was forecast to strengthen into a Category 1 hurricane, the lowest on the five-step Saffir-Simpson scale of hurricane intensity, with top winds of 145km/h. While that would be well below the intensity of Katrina, a powerful Category 3 storm, the vast size of Isaac's slow-moving system has forecasters predicting widespread flooding.
“Even if it is a tropical storm at landfall, the large size of it will still generate significant storm surge,” Hurricane Center Director Rick Knabb told reporters. “That is life-threatening potentially.”
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 in search of higher ground. Others prepared, or were forced, to ride the storm out.
“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,” she said.
Along Canal Street in New Orleans' historic French Quarter, crews were boarding up the windows of some stores and businesses.
“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'd taken care to stock up on food and water at home and fuel his generator.
Isaac was centered 235km southeast of the mouth of the Mississippi River early Tuesday with top sustained winds of 110km/h - a speed that places the storm very near hurricane status - and swirling northwest at 19km/h.
The storm was more than 645km wide and Craig Fugate, director of the Federal Emergency Management Agency, said the worst effects may well be in Mississippi and Alabama.
After Katrina, the US 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 seven years ago.
Lt. Gen. Russel Honore, who led post-Katrina recovery efforts, said the levees and the level of local government preparedness are “a different story” from 2007.
“But on any given day Mother Nature can beat us,” he told CNN, warning the storm could be potent. Isaac has “the capacity to turn the lights out in New Orleans,” he said.
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.
Energy companies evacuated offshore oil rigs and shut down US Gulf Coast refineries as the storm threatened to batter the country's oil refining belt.
Oil firms ferried workers in helicopters from oil platforms hundreds of kilometres offshore in the Gulf of Mexico.
As a precaution, as of Monday afternoon, the energy industry had shut down 78 percent of Gulf of Mexico crude production and 48 percent of its natural gas production, government figures showed.
Despite the threat to the US offshore oil patch, which produces about 23 percent of the country's oil output and 7 percent of its natural gas, prices for international benchmark Brent crude traded down $1.24 to $112.35 a barrel in late Monday activity.
Once ashore, the storm could wreak havoc on low-lying fuel refineries along the Gulf Coast that account for about 40 percent of US refining capacity.
Louisiana Governor Bobby Jindal said President Barack Obama approved his state's request for a federal disaster declaration, on Monday. Obama's approval, given in a phone call that included the governors of Mississippi and Alabama, makes federal funds available for disaster recovery activities like clearing debris.
The ports of Mobile and New Orleans were closed and barge traffic was suspended along southern portions of the Mississippi River.
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. - Reuters