Updated

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 3 hurricane by Thursday, menacing a broad swath of the Gulf Coast. Katrina was a Category 3 storm when it ravaged New Orleans a year ago Tuesday.

Weary residents kept an eye on the forecast.

Bari Landry, who lives in a neighborhood 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 Saturday.

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.

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 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.

Ernesto attracted attention during a weekend of events marking the anniversary of Katrina. Driving rain soaked people gathered outside the Superdome for one observance, but the storms were not related to Ernesto.

Strock appeared with Blanco and Donald Powell, chairman of President Bush's Gulf Coast rebuilding office, at a news conference to show off new protections since Katrina, including flood gates that can be dropped into the mouths of three large canals to reduce the effect of water surging out of Lake Ponchartrain.

However, some of the most substantial work planned on the levee system won't be done for the next couple of years.

Col. Richard Wagenaar, who oversees the New Orleans district of the Corps, said the flood control system, which was breached in three places after Katrina, was equal to or better than it was when Katrina struck, but he said he and his staff had already begun making preparations for Ernesto.

Wagenaar said he would have to weigh all the risks in any decision to close the flood gates. When they are closed, it takes longer to pump rain water out of the city's low-lying areas, creating risks of rain flooding.

Blanco said that although she is not happy with the current strength of the levee system, she believes as much work as possible has been done in the year since Katrina.

"I will feel better when they are fully functional and complete, but it will take time," Blanco said. "We've gotten as far as we could get in one year."