National Guard troops stand ready, batteries and water bottles are selling briskly, and one small-town mayor has spent a sleepless night worrying. The New Orleans area is skittishly watching as a storm marches across the Caribbean on the eve of Hurricane Katrina’s third anniversary.

With forecasters warning that a strengthening Gustav could slam into the Gulf Coast as a major hurricane, a New Orleans still recovering from Hurricane Katrina’s devastating hit drew up evacuation plans.

“I’m panicking,” said Evelyn Fuselier of Chalmette, whose home was submerged in 14 feet of floodwater when Katrina hit. Fuselier said she’s been back home only a year and nervously watched as Gustav swirled toward the Gulf of Mexico. “I keep thinking, ’Did the Corps fix the levees?,’ ’Is my house going to flood again?’ ... ’Am I going to have to go through all this again?”’

Taking no chances, city officials began preliminary planning to evacuate and lock down the city in hopes of avoiding the catastrophe that followed Katrina in 2005.

New Orleans Mayor Ray Nagin left the Democratic National Convention in Denver to return home for the preparations. Gov. Bobby Jindal declared a state of emergency to lay the groundwork for federal assistance, and put 3,000 National Guard troops on standby.

Forecasters said Wednesday that Gustav could strengthen to a Category 3 hurricane with winds of 111 mph or higher in coming days before hitting somewhere between the Florida Panhandle and Texas.

If a Category 3 or stronger hurricane comes within 60 hours of the city, New Orleans plans to institute a mandatory evacuation order. Unlike Katrina, there will be no massive shelter at the Superdome, a plan designed to encourage residents to leave. Instead, the state has arranged for buses and trains to take people to safety.

It was unclear what would happen to stragglers. Jerry Sneed, the city’s emergency preparedness director, said officials are ready to move about 30,000 people. Nearly 8,000 people had signed up for transportation help by late Wednesday. Hurricane Katrina struck New Orleans on Aug. 29, 2005, its storm surge blasting through the levees that protect the city. Eighty percent of the city was flooded.

The Army Corps of Engineers has since spent billions of dollars to improve the levee system, but because of two quiet hurricane seasons, the flood walls have never been tested.

Robert Turner Jr., the regional levee director, said the levee system can handle a storm with the likelihood of occurring every 30 years, what the corps calls a 30-year storm. By comparison, Katrina was a 396-year storm.