After making landfall Tuesday as a Category 1 hurricane in southeastern Louisiana, Tropical Storm Isaac’s slow crawl northward from the Gulf Coast is causing significant flooding and some wind damage, as well as a threat of tornadoes.
“The slow motion has been exacerbating the problem here,” said Keith Blackwell, meteorologist at the University of South Alabama’s Coastal Weather Research Center in Mobile. “It just won’t leave.”
Isaac came ashore late Tuesday afternoon with 80 mph winds near the mouth of the Mississippi River. The storm weakened some after landfall, but as of 11 a.m. today still had tropical-storm-force winds of 40 mph. The storm’s center was about 100 miles north-northwest of Baton Rouge, Louisiana and was moving north-northwest at about 9 mph.
The storm is expected to continue weakening, but will bring heavy rains to the upper Midwest early next week.
The National Hurricane Center in Miami released a bulletin this morning warning of a “significant” flood threat as Isaac moves slowly northward during the upcoming Labor Day weekend. The storm could bring seven to 14 inches of rain during its trek, and some places may see as much as 25 inches before Isaac has departed.
The NHC also warned of high water levels along the Gulf Coast. And although Isaac is weakening, the NHC noted that the threat of tornadoes being spun off the storm is increasing.
Bob Wagner, a meteorologist at the Baton Rouge-New Orleans National Weather Service office in Slidell, Louisiana, said flooding could continue in his area for two days or longer.
The “extremely heavy rainfall” from Isaac has caused serious flooding problems in southeastern Louisiana, Wagner said.
“I’m not aware of any people on rooftops, but there’s water in homes, roads are closed, and there’s a signficant amount of water in some neighborhoods,” Wagner said.
The New York Times reported today that New Orleans had escaped “major damage” from Isaac, but that much of the city is without power because of fallen trees.
Keith Williams, a meteorologist at the National Weather Service office in Mobile, said some areas of southeastern Mississippi had received as much as 17 inches of rain. Tornado watches have been issued for much of the Gulf Coast, including Mobile, Williams said.
Blackwell, the Coastal Weather Research Center meteorologist, said Isaac’s slow movement as it made landfall had pushed saltwater far into the drought-depleted Mississippi River. The Times-Picayune newspaper of New Orleans reported that locally maintained levees have failed and caused flooding in Plaquemines Parish, Louisiana, where the Mississippi flows into the Gulf of Mexico.
Blackwell said Isaac’s low-rating as a Category 1 hurricane on the Saffir-Simpson scale — which rates hurricanes from one to five based on their wind speeds and destructive potential — was misleading. The storm was gaining strength as it came ashore, he said.
“Isaac wasn’t more severe than was anticipated, but it could have been much worse,” Blackwell said.
Willie Drye has been writing about hurricanes and other topics for National Geographic News since 2003. Visit his blog, Drye Goods.