Tropical Storm Isaac swirled toward Louisiana, prompting Gulf Coast states to issue states of emergency seven years after Hurricane Katrina devastated New Orleans.
Severe flooding may pose a higher threat than high winds, officials told the New York Times. The National Weather Service predicted that the storm would become a hurricane by Tuesday night or Wednesday morning.
The storm was lashing the Florida coast and with winds reaching 65 miles (105 kilometers) per hour. The storm has killed 21 people -- 19 in Haiti alone, The Associated Press reported -- as it has churned on a northwesterly route over the past several days.
Rick Knabb, director of the National Hurricane Center, explained to reporters this morning that because it is a slow-moving storm, Isaac poses major flooding concerns. Knabb said the storm is likely to arrive on U.S. land as a Category One or even a tropical storm, it is nonetheless a very large and slow storm and has the potential to dump lots of water.
Knabb said the storm could unleash up to a foot of rain in some areas and is likely to cause storm surge between 6 to 12 feet.
The storm surge, he said, could range between 6 to 12 feet along the coastline in Alabama, Missisippi and southeastern Louisiana.
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.
"Under current forecasts, New Orleans may feel winds as early as Monday night, with heavy weather Tuesday and Wednesday," New Orleans 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's latest forecast said Isaac was 530 miles off the mouth of the Mississippi River as it moved away from Key West, Florida.
It was heading west-northwest toward Louisiana at 15 miles per hour and a hurricane warning was in place for populated areas including New Orleans.
"A hurricane warning means that hurricane conditions are expected somewhere within the warning area," the NHC said.
"Preparations to protect life and property should be rushed to completion."
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 its gathering in Tampa.
The shortened convention will nominally open on Monday but immediately adjourn and reconvene on Tuesday, with speeches on Wednesday -- by when Louisiana could be in the eye of the storm -- and end on Thursday.
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.