NEW ORLEANS (AP):

What was to have been a weekend of remembrance of Hurricane Katrina's destruction became a weekend of worry as 'Ernesto' strengthened to a hurricane in the Caribbean.

The National Hurricane Center said Ernesto could grow into a Category Three hurricane by Thursday, menacing a broad swath of the Gulf Coast. 'Katrina' was a Category Three storm when it ravaged New Orleans a year ago tomorrow.

Weary residents kept an eye on the forecast.

Bari Landry, who lives in a neighbourhood heavily flooded by Katrina, said she reserved a hotel room in Houston for Thursday through Saturday.

"There may be panic, but we know the drill," she said.

Gov. Kathleen Blanco said state officials were keeping an eye on Ernesto, and the Army Corps of Engineers was carefully tracking the storm's movement, said Lt. Gen. Carl Strock, head of the Army Corps.

Early test

It was too early to tell whether Ernesto would provide an early test for the city's levee system, which Strock conceded may not yet be strong enough to withstand a large storm surge.

Strock said he was confident the Corps had done all it could to repair and reinforce 220 miles (350 kilometres) of levee walls, but said many variables would determine whether the levees could withstand a major hurricane.

Much would depend on where the hurricane made landfall, wind speed, rainfall and other factors, he said. The biggest concern would be water levels so high that they could cascade over the levee walls, weakening them to the point of breaching.

"It's critical we make the right call for the right reason," Blanco said, cautioning that officials want to ward off the chance of unnecessary evacuations.

Mandatory evacuation in the parishes below New Orleans would kick in when the storm was 50 hours from the coast, New Orleans Homeland Security chief Terry Ebbert said. New Orleans would begin mandatory evacuation at the 40-hour mark.

The city already has buses and trains under contract to evacuate people without the means to leave, he said.