NEW ORLEANS – A large storm system churning in the Gulf Of Mexico grew Friday into Tropical Storm Lee, beginning a Labor Day weekend-long assault that could bring up to 20 inches of rain in some spots from Louisiana to the Florida Panhandle.

The storm was expected to make landfall on the central Louisiana coast late today and turn east toward New Orleans, where it would provide the biggest test of rebuilt levees since Hurricane Gustav struck on Labor Day 2008.

Residents who have survived killer hurricanes such as Betsy, Camille and Katrina didn’t expect Lee to live up to that legacy.

“It’s a lot of rain. It’s nothing, nothing to Katrina,” said Malcolm James, 59, a federal investigator in New Orleans who lost his home after levees broke during Katrina in August 2005 and had to be airlifted by helicopter.

“This is mild,” he said. “Things could be worse.”

Lee comes less than a week after Hurricane Irene killed more than 40 people from North Carolina to Maine and knocked out power to millions. It was too soon to tell if Hurricane Katia, out in the Atlantic, could endanger the United States.

By Friday evening, the outer bands of Lee, the 12th named storm of the Atlantic hurricane season, already began dumping rain over southeastern Louisiana, southern Mississippi and Alabama.

The storm’s biggest impact, so far, has been in the Gulf of Mexico oil fields. About half of the Gulf’s normal daily oil production has been cut as rigs were evacuated, although oil prices were down sharply Friday on sour economic news.

Federal authorities said 169 of the 617 staffed production platforms have been evacuated, along with 16 of the 62 drilling rigs. That’s reduced daily production by about 666,000 barrels of oil and 1.7 billion cubic feet of gas.

Kevin Lucas, an offshore worker from Lafayette, La., was evacuated Thursday by boat from a production platform. He was in the New Orleans’ French Quarter on Friday. “It was rocking,” he said of the boat. “A few fellows got seasick.”

Tropical storm warning flags were flying from Mississippi to Texas and flash flood warnings extended along the Alabama coast into the Florida Panhandle.

The National Hurricane Center said the center of Lee was about 180 miles west-southwest of the mouth of the Mississippi River on Friday and moving north at just 3 mph.

Governors in Louisiana and Mississippi, as well as the mayor of New Orleans, declared states of emergency. Officials in several coastal Louisiana and Mississippi communities called for voluntary evacuations.