Forecasters warned that Gustav could grow into a dangerous Category 3 hurricane in the next several days. By Labor Day, Gustav could make landfall anywhere from south Texas to the Florida panhandle, and hurricane experts said everyone in between should be concerned.
"We know it's going to head into the Gulf. After that, we're not sure," said meteorologist Rebecca Waddington at the National Hurricane Center in Miami. "For that reason, everyone in the Gulf needs to be monitoring the storm."
For New Orleans residents, the warnings take on an added sense of urgency.
"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 in her home one year this month, and called watching Gustav swirl toward the Gulf of Mexico indescribable. "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 the 2005 storm. 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.
Post Katrina, rebuilding walls and rebuilding trust has been the task of the Army Corps of Engineers, reports CBS News correspondent Hari Sreenivasan. They've accomplished a lot - but it may not be enough.
"We've repaired 220 miles of the approximately 350 miles of levees and floodwalls that encompass the greater New Orleans area," Randy Cephus of the Army Corps of Engineers told Sreenivasan. "Our charter was to have this complete by 2011; we're not there yet."
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.
At a suburban Lowe's store, employees said portable generators, gasoline cans, bottled water and batteries were selling briskly. Hotels across south Louisiana reported taking many reservations as coastal residents looked inland for possible refuge.
Steve Weaver, 82, and his wife stayed for Katrina - and were plucked off the roof of their house by a Coast Guard helicopter. This time, Weaver has no inclination to ride out the storm.
"Everybody learned a lesson about staying, so the highways will be twice as packed this time," Weaver said.
Katrina struck New Orleans on Aug. 29, 2005, and its storm surge blasted through the levees that protect the city. Eighty percent of the city was flooded.
Though pockets of the New Orleans are well on the way to recovery, many neighborhoods have struggled to recover. Many residents still live in temporary trailers, and shuttered homes still bear the 'X' that was painted to help rescue teams looking for the dead.
Many people never returned, and the city's population, around 310,000 people, is roughly two-thirds what it was before the storm, though various estimates vary wildly.
Since the storm, the Army Corps of Engineers has spent billions of dollars to improve the levee system, but because of two quiet hurricane seasons, the flood walls have never been tested.
Floodgates have been installed on drainage canals to stop any storm surge from entering the city, and levees have been raised and in many places strengthened with concrete.
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.