Tropical Storm Isaac took aim at Louisiana and other US Gulf states Monday, prompting them to declare states of emergency almost seven years after Hurricane Katrina devastated New Orleans.
The storm was lashing the Florida coast and with winds reaching 65 miles (100 kilometers) per hour, it could reach hurricane force in about 24 hours, the Miami-based National Hurricane Center warned.
Early Monday, Isaac was churning 75 miles (120 kilometers) west-southwest of Key West, Florida, heading across the warm waters of the Gulf of Mexico, where it was expected to gather strength.
Louisiana, Mississippi and Alabama issued emergency warnings on Sunday, 24 hours after Isaac forced the main program of the US Republican convention in Tampa, Florida, to be curtailed by one day.
Ahead of Isaac's expected landfall Tuesday or Wednesday along the Gulf Coast, Alabama Governor Robert Bentley ordered mandatory evacuations in the southern counties of Mobile and Baldwin, while Louisiana Governor Bobby Jindal recommended voluntary evacuations within the hurricane watch area.
The NHC's latest forecast said Isaac was still 510 miles (820 kilometers) southeast of the mouth of the Mississippi River.
It was heading west-northwest toward Louisiana at 14 miles (22 kilometers) per hour and a hurricane warning was in place for populated areas including New Orleans.
"Under current forecasts, New Orleans may feel winds as early as Monday night, with heavy weather Tuesday and Wednesday," the city's mayor, Mitch Landrieu, said in a statement, noting that a state of emergency declaration there would help city officials prepare for the worst.
The NHC said "preparations to protect life and property should be rushed to completion," in all areas subject to the hurricane warning.
Hurricane Katrina made landfall along the Mississippi-Louisiana border on August 29, 2005 -- eventually killing around 1,800 people in New Orleans, a city famed for its jazz music, easygoing atmosphere and Creole cuisine.
Although 1.4 million residents and visitors were ordered to evacuate as the monster storm approached, many could not or would not and were left stranded.
A lack of preparation and bungled coordination forced residents to take shelter in attics, and then break through their roofs to escape rising water.
Sunday's emergency declarations indicated the importance of official efforts to safeguard the city, as Isaac brought rain and choppy seas to the Florida Keys after battering Haiti and Cuba over the weekend.
"Some strengthening is forecast during the next 48 hours and Isaac is expected to become a hurricane in a day or two," the NHC said.
A hurricane warning for the Florida Keys and parts of the state's southwest coast was reduced to a tropical storm warning, though Republicans had already postponed the planned Monday start of their gathering in Tampa.
The NHC also warned that that Isaac could spawn "isolated tornadoes" over Central and Southern Florida on Monday.
The delegate roll call for Mitt Romney to be formally nominated to take on President Barack Obama in the November 6 election will now take place Tuesday, after Monday's program was repackaged into a tighter schedule due to the storm.
Party officials stressed that the prime nighttime speaking slots on Tuesday, Wednesday and Thursday, including speeches by Romney, his wife Ann and running-mate Paul Ryan, remained unchanged.
But although the show in Tampa will go on, Louisiana could be in the eye of the storm by Tuesday or Wednesday, depriving Republicans of the spotlight.
Footage of desperate Americans in New Orleans, waving signs reading "Help Us," horrified people at home and abroad in 2005, while in the Lower Ninth Ward -- the poorest part of the city -- built in a basin and 99 percent black, bodies drifted lifelessly with the floodwater.
Many fled to the Superdome, the stadium where 10,000 people displaced by the hurricane had already sought refuge, but it too became cut off by the water.
Finally, the National Guard was deployed, and managed to restore a semblance of order, helping coordinate airlifts and bus evacuations that scattered survivors across the country.