Tropical Storm Isaac strengthened into a hurricane just off the US Gulf Coast on Tuesday as it churned toward landfall in the New Orleans area seven years after the city was devastated by Hurricane Katrina. Isaac's winds, rain and storm surge could pose a major test of New Orleans' new flood control systems and reinforced levees. Forecasts from the US National Hurricane Center showed the storm coming ashore late on Tuesday.
"Isaac has finally formed into a hurricane, so we are officially in the fight and the city of New Orleans is on the front lines," New Orleans Mayor Mitch Landrieu told reporters. The US Army Corps of Engineers began to close for the first time the massive new floodgate on the largest storm-surge barrier in the world, at Lake Borgne, east of New Orleans.
In other preparations, energy companies evacuated offshore oil rigs and shut down US Gulf Coast refineries as the storm threatened to batter the oil refining belt. At 11:20 am EDT (1520 GMT), the Hurricane Center said Isaac was centered about 75 miles (120 kilometres) south-south-east of the mouth of the Mississippi River with top sustained winds of 75 miles per hour (120 kph).
Its forward speed was a relatively slow 10 mph (16 kph), a concern for people in the path of the storm since slow-moving cyclones can bring higher rainfall totals. The storm was about 370 miles (595 km) wide. Isaac spared Tampa, Florida, where the Republican National Convention began on Monday. But it forced party leaders to revamp their schedule and they may have to make further revisions so as not to be seen celebrating Mitt Romney getting the party's presidential nomination while Gulf Coast residents are struggling through the storm.
President Barack Obama added his concerns in a statement from the White House, saying: "We're dealing with a big storm and there could be significant flooding and other damage across a large area. "Now is not the time to tempt fate," he added, saying people should heed warnings and evacuate if instructed by authorities to do so.
Rain and high winds were expected in the Gulf Coast region in the coming hours, bringing the threat of storm surge and flooding. 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. After Katrina, the 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.
The floodgate being closed is 26 feet (8 meters) high and 1.8 miles (2.9 km) long. It was designed to prevent the Inner Harbor Navigation Canal from breaching its walls, as it did in 2005, flooding the neighbourhoods of the Lower Ninth Ward, Gentilly and New Orleans East, and St. Bernard Parish.
Most of the Lower Ninth, which still shows the devastation of Katrina, was deserted and quiet about midday on Tuesday. Residents who hadn't evacuated were unloading water, food and fuel from their cars and trucks into their homes. Authorities have urged thousands of residents in low-lying areas to leave, warning the storm could flood towns and cities in at least three US Gulf Coast states with a storm surge of up to 12 feet (3.7 meters).
Rainfall accumulations, potentially totalling as much as 20 inches (50 cm) in some areas, could also trigger widespread flooding. Isaac was not forecast to strengthen beyond a Category 1 hurricane, the lowest on the five-step Saffir-Simpson scale. Its top projected winds were about 80 mph (129 kph). Isaac killed at least 22 people and caused significant flooding and damage in Haiti and the Dominican Republic before skirting the southern tipof Florida on Sunday.