Isaac made landfall Tuesday night on the southeastern Louisiana coast as a Category 1 hurricane with winds of 80 mph.
Arriving on the eve of the seventh anniversary of Hurricane Katrina, Isaac is the first hurricane to hit the Gulf Coast since Ike in 2008.
Isaac's core is expected to pass west of New Orleans with winds close to 80 mph and head for Baton Rouge. Winds could gust up to 100 mph at times, which could affect tall buildings in New Orleans. The hurricane is expected to gradually weaken, but only after dumping 7 to 14 inches of rain across the state, with some places receiving up to 20 inches.
WHAT DOES MAKE LANDFALL MEAN?
A hurricane is considered to have made landfall when the center or eye intersects with a coastline.
The strongest winds are often not in the center of a hurricane. They are usually on the storms outer bands that come ashore before and after the eye. Sometimes an uneasy calm actually is felt when the eye passes over, but it is often followed by more strong winds and rain.
While people across the coast were boarding up their homes to prepare for damaging winds, the even bigger fear is potential flooding.
The greatest concern is an expected storm surge of between 6 and 12 feet off the Louisiana and Mississippi coasts, 4 to 8 feet along the Alabama coast and 3 to 6 feet on the Florida Panhandle. Storm surge is when hurricane winds raise sea levels off the coast, causing flooding on land.
In the Big Easy, residents hunkered down behind levees fortified after Katrina.
Isaac already left a trail of destruction in the Caribbean, most of it blamed on flooding that killed 24 people.
REPUBLICAN NATIONAL CONVENTION
Isaac veered well west of the Republican National Convention site in Tampa, but it was soggy over the weekend in the bayside city. The GOP pushed back the start of speeches a day to Tuesday and protesters' ranks have been small, in part because of the soaking brought on by Isaac and in part because of the huge police presence in the city.
The storm has also altered some Republican governors' plans to attend. Florida Gov. Rick Scott canceled a speaking engagement, and Louisiana Gov. Bobby Jindal and Alabama Gov. Robert Bentley canceled their trips to Tampa.
Officials in Louisiana's St. Charles Parish near New Orleans and Terrebonne Parish that includes Houma closer to the Gulf have told about 73,000 residents total to leave ahead of the storm. Some coastal residents in Alabama have also been told to evacuate.
However, officials haven't ordered the kind of evacuations that have in the past clogged interstates, with both sides of the highway heading one direction. In New Orleans, Mayor Mitch Landrieu said evacuations would not be ordered and told residents to prepare carefully and ride it out.