Hurricane Warnings Issued as Isaac Heads for Gulf Coast

Late into Monday night, updated forecasts called for Tropical Storm Isaac to turn into a Category 1 hurricane and it was expected to hit a stretch of the Gulf Coast between the Florida panhandle and New Orleans sometime late Tuesday or early Wednesday — the latter putting it an eerie seven years to the day after Hurricane Katrina devastated The Big Easy.

The storm was on the verge of becoming a hurricane, and the slow-moving system was sitting approximately 200 miles southeast of the mouth of the Mississippi River.

Rick Knabb, director of the National Hurricane Center, said that Isaac was “life-threatening” and that the most serious danger from it were storm surges from the huge amounts of water it will bring, and not the strong winds. “A slow-moving, large system poses a lot of problems,” Knabb said.

As New Orleans and Louisiana braced for Isaac, President Barack Obama declared a state of emergency for the entire state. 

New Orleans itself hasn’t been ordered to evacuate; the levees that were breached by Katrina have been rebuilt, and they’re expected to hold back a storm surge that could reach 12 feet. (The surge of nearly 28 feet that came along with Katrina was largely responsible for the 1,500 or so deaths the storm caused).

Credit: NOAA

Residents of St. Charles and Plaquemines Parishes, however, which lie outside the city, are now under mandatory evacuation orders. Gov. Bobby Jindal, meanwhile, declared a state of emergency, urging voluntary evacuations all along the coast.

Jindal has also postponed his scheduled Tuesday speech at the Republican National Convention in Tampa, saying he might speak Wednesday if Louisiana is in reasonably good shape. The convention itself should be far less severely impacted by Isaac than weather experts originally feared.

But while Louisiana is currently in Isaac’s crosshairs, two days are an eternity in the life of a hurricane: the storm could change course, so the governors of Mississippi and Alabama have declared states of emergency for their coasts as well, where the storm surge could reach 6 feet even if Isaac stays on its current course.

Although Isaac hadn’t graduated to full hurricane status as of Monday, the chances were good that it would: hurricanes draw their energy from warm ocean waters, and the Gulf of Mexico is warm enough to suggest an upgrade before the storm makes landfall. 

Intensity forecasts, however, are notoriously unreliable and forecasters were calling for Isaac to either be a Category 1 or Category 2 hurricane and reach landfall by late Tuesday night.

That’s the good news; the bad news, suggested Weather Underground’s Bryan Norcross, is that Isaac’s large size and relatively slow forward motion could make landfall a dangerously drawn-out affair.

“People will experience strong, howling winds and torrential rain for 24-to-36 hours or more in this scenario,” Norcross wrote. Total rainfall could range from 10-20 inches or more along the coast, with heavy rainfall extending all the way from Arkansas to the Carolinas as Isaac moves over land.