Tropical Storm Isaac moved into the Gulf of Mexico late Sunday, setting the stage for a midweek rendezvous with the northern Gulf coast.
In response to the growing threat, the National Hurricane Center issued hurricane warnings for the coast from Morgan City, La., to Destin, Fla.
Forecasters said it remained difficult to determine the storm's most likely track, but New Orleans was in the middle of the hurricane center's "cone of uncertainty."
Louisiana Gov. Bobby Jindal called a state of emergency on Sunday and suggested that people leave low-lying parts of the state. A voluntary evacuation of New Orleans began Sunday, and mandatory evacuations could begin as early as Monday.
An emergency declaration was also issued in Mississippi by Gov. Phil Bryant amid concerns of storm surge threatening low-lying areas.
By late Sunday Isaac remained a powerful tropical storm, with 65-mph sustained winds, and forecasters anticipated it would grow into a hurricane by Monday. The official forecast predicts Isaac will come ashore as a Category 2 hurricane along the northern Gulf of Mexico coast, although some forecast models strengthened it into a major hurricane before landfall.
Isaac could reach the northern Gulf coast by Wednesday -- the seventh anniversary of Hurricane Katrina.
Passing through the Florida Keys as a tropical storm, Gov. Rick Scott said Sunday evening that only minor damage was reported in Florida.
In Tampa, Republican National Convention officials said they would convene briefly on Monday, then recess until Tuesday afternoon, when the storm was expected to have passed.
Offshore, energy companies were preparing for the storm, as they stepped up evacuation of workers from the Gulf and shut down some production.
By midday Sunday, the Bureau of Safety and Environmental Enforcement reported 24 percent of the current daily oil production in the Gulf had been shut down, along with just over 8 percent of current daily natural gas production.
Satish Nagarajaiah, a professor of civil and environmental engineering at Rice University, said the evacuations and production shutdowns were routine. More platforms will be shut down by Monday, he said, most of them in the eastern Gulf. And once the storm passes, production will be restarted quickly unless the platform sustains damage, he said.
Drilling in federal waters of the Gulf of Mexico accounts for 23 percent of domestic crude oil production and about 7 percent of natural gas production, according to U.S. government statistics.
More than 40 percent of the country's refining capacity is located along the Gulf coast, too. So far, refineries are continuing operations.
BP said Sunday it had temporarily suspended production at all of its operated production platforms in the Gulf. Apache Corp. and Anadarko Petroleum Corp. both said they shut in some production. BP had begun evacuating workers Friday; by Saturday, Chevron, Murphy Oil, Shell, Exxon Mobil and other companies were evacuating nonessential workers.
On Sunday afternoon some forecast models suggests Isaac could move as far west as the Texas-Louisiana border before moving inland, possibly posing a hurricane threat to Texas.
But that scenario remained unlikely, forecasters said. "There's not a zero percent chance on Texas, but it certainly is still an outlier" that the state would get hit, said Bill Read, the recently retired director of the National Hurricane Center.
Depending how close Isaac moves to Texas, waters offshore Galveston could see some higher waves, and winds could rise over the region on Wednesday and Thursday. Some rain is also possible.
Staff writer Jeannie Kever contributed to this report.
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