NEW ORLEANS // Hurricane Gustav charged across the Gulf of Mexico today as residents fled New Orleans and the National Guard prepared to patrol evacuated neighborhoods in a city still recovering three years after Katrina struck. Gustav dropped from a Category 4 to a Category 3 storm overnight, but forecasters warned it could gain strength from the gulf's warm waters before making landfall as early as Monday. Long before Mayor Ray Nagin's mandatory evacuation order took effect on Sunday morning for the city's vulnerable West Bank, residents were already streaming out of New Orleans and other communities along the Gulf Coast. Bumper-to-bumper traffic was reported in nearly every direction out of New Orleans, and on Bourbon Street, where the party seemingly never ends, only stragglers toting luggage were sporadically seen on the sidewalks. Gustav crossed western Cuba on Saturday and has already killed more than 80 people in the Caribbean. It picked up speed upon reaching the gulf and was moving northwest at 27kph with winds of 193kph, according to the National Hurricane Center's latest update. Hurricane-force winds extended 80km from the storm's centre which was about 523km south-east of the Mississippi River's mouth. The storm could bring a surge of up to 20 6 metres to the coast and rainfall totals of up to 38cm. A hurricane warning was issued for over 800km along the Gulf Coast from Cameron, Louisiana, near the Texas border to the Alabama-Florida state line, meaning hurricane conditions are expected there within 24 hours. The White House said President George W Bush's plans to attend the Republican National Convention on Monday were on hold because of worries about Gustav. Mr Bush had been scheduled to speak late Monday night in St Paul, Minnesota. He planned to get an update on preparations for the storm from disaster relief officials and state and local representatives later on Sunday. The Bush administration was severely criticised for its tardy response to Katrina three years ago. Homeland Security Secretary Michael Chertoff planned to travel to Louisiana to observe preparations. And the likely Republican presidential nominee John McCain and his running mate, the Alaska governor Sarah Palin, were traveling to Mississippi. In New Orleans, Mr Nagin used stark language to urge residents to get out of the city, calling Gustav "the mother of all storms". "This is the real deal, not a test," he said, as he issued the evacuation order on Saturday night. "For everyone thinking they can ride this storm out, I have news for you: that will be one of the biggest mistakes you can make in your life." Forecasters were slightly less dire in their predictions, saying the storm should make landfall somewhere between western Mississippi and east Texas, where evacuations were also under way. It is too early to know whether New Orleans will take another direct hit. The mandatory evacuation of the West Bank, where levee improvements remain incomplete, began at 8am local time, with the east bank to follow later on Sunday. It is the first test of a revamped evacuation plan designed to eliminate the chaos, looting and death that followed Katrina. Still, there were a few people holding out. "You'd be a moron" not to be worried about the storm, Inez Douglas said at Johnny White's Sports Bar & Grill. But while she was keeping an eye on the storm, she was not going anywhere. An estimated one million people fled the Gulf Coast on Saturday by bus, train, plane and car. They clogged roadways, emptied petrol stations of fuel and jammed phone circuits. *AP