WASHINGTON -- Federal officials warned Tuesday that slow-moving Hurricane Isaac could pummel southern Louisiana and neighboring states for more than two days, causing significant storm surge along parts of the Gulf Coast, dumping enough rain to cause widespread flooding, and spawning destructive tornadoes.
"As the center of the storm comes ashore tonight, that will not be the end of the event, it will be just the beginning," Rick Knabb, director of the National Hurricane Center, told reporters on a conference call.
Hurricane Isaac presents a "significant heavy rainfall hazard" because it is moving at only 10 mph, meaning it will linger longer than most hurricanes, Knabb said. Up to 20 inches could douse some areas, and heavy rain will likely fall hundreds of miles inland, he said.
The hurricane could send Gulf of Mexico waters surging as high as 6 to 12 feet above normal along the coasts of Louisiana, Mississippi and Alabama, officials said. They have issued tornado warnings to communities east of the expected landfall.
For many, the time to get out of the storm's path has "come and gone," Knabb said. He urged residents to listen carefully to evacuation and other emergency orders.