Hurricane Isaac makes landfall in La.

Updated at 10:41 p.m. ET

(CBS/AP) NEW ORLEANS - Hurricane Isaac spun into the southern Louisiana coast late Tuesday, sending floodwaters surging and unleashing fierce winds, as residents hunkered down behind boarded-up windows. New Orleans calmly waited out another storm on the eve of Hurricane Katrina's seventh anniversary, hoping the city's strengthened levees will hold.

Isaac, a massive storm spanning nearly 200 miles from its center, made landfall at about 6:45 p.m. near the mouth of the Mississippi River. But it was zeroing in on New Orleans, about 75 miles to the northwest, turning streets famous for all-hours celebrations into ghost boulevards.

While many residents stayed put, evacuations were ordered in low-lying areas of Louisiana and Mississippi, where officials ordered the closure of the state's 12 shorefront casinos. By late Tuesday, more than 100,000 homes and businesses had lost power.

Ed Rappaport, deputy director of the National Hurricane Center, said Isaac's core would pass west of New Orleans with winds close to 80 mph and head for Baton Rouge.

"On this course, the hurricane will gradually weaken. Its winds will come down," Rappaport said Tuesday night from the Miami-based center. He said gusts could reach about 100 mph at times, especially at higher levels which could damage high-rise buildings in New Orleans.

As Isaac neared the city, there was little fear or panic. With New Orleans' airport closed, tourists retreated to hotels and most denizens of a coastline that has witnessed countless hurricanes decided to ride out the storm.

"Isaac is the son of Abraham," said Margaret Thomas, who was trapped for a week in her home in New Orleans' Broadmoor neighborhood by Katrina's floodwaters, yet chose to stay put this time. "It's a special name that means `God will protect us'."

The storm drew intense scrutiny because of its timing — just before the anniversary of the hurricane that devastated that city, while the first major speeches of the Republican National Convention went on in Tampa, Fla., already delayed and tempered by the storm

"We don't expect a Katrina-like event, but remember there are things about a Category 1 storm that can kill you," New Orleans Mayor Mitch Landrieu said, urging people to use common sense and to stay off any streets that may flood.

Other officials, chastened by memories and experience, advised caution. Tens of thousands of people were told to leave low-lying areas, including 700 patients of Louisiana nursing homes. At least one tornado spun off of Isaac in Alabama, but there were no immediate reports of damage or injuries.

Many residents along the Gulf Coast opted to ride it out in shelters or at home and officials, while sounding alarm about the dangers of the powerful storm, decided not to call for the mass evacuations like those that preceded Katrina, which packed 135 mph winds in 2005.

"We don't expect a Katrina-like event, but remember there are things about a Category 1 storm that can kill you," Landrieu said, urging people to use common sense and to stay off any streets that may flood.

Obama on Isaac: "Now is not the time to tempt fate"
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Isaac offers one of the first tests of a New Orleans levee system bolstered after the catastrophic failures during Hurricane Katrina. But calm prevailed in the city Tuesday as residents sized up the threat.

"I feel safe," said Pamela Young, who settled in to her home in the Lower 9th Ward -- a neighborhood devastated by Katrina -- with dog Princess and her television, waiting for the storm. "Everybody's talking `going, going,' but the thing is, when you go, there's no telling what will happen. The storm isn't going to just hit here."

Young, who lives in a new, two-story home built to replace the one destroyed by Katrina, said she wasn't worried about the levees.

"If the wind isn't too rough, I can stay right here," she said, tapping on her wooden living room coffee table. "If the water comes up, I can go upstairs."

On the "CBS Evening News," chief meteorologist David Bernard of CBS Miami station WFOR-TV said the tropical storm conditions are spreading not only the New Orleans area, but all across the Gulf Coast and the Mississippi, and also into Alabama. The latest advisory from the Hurricane Center has it as an 80 mph storm, about 100 miles southeast of New Orleans, and it's going to slowly move across the state Wednesday and then also into Thursday afternoon, shaping up to be a really slow mover.

WFOR Miami's interactive storm tracker

In New Orleans, Landrieu insisted the city was ready, CBS News correspondent Byron Pitts reports. When asked about the comfortable and confident stance people have about the storm - and if that's a good place to be - Landrieu said, "I think what they're comfortable and confident in is that, given the level of this storm, that the levees can hold and we're not gonna have a Katrina event."

In Cocodrie, La., the biggest concern was the expected storm surge, CBS News correspondent Manuel Bojorquez reports. Two major flood gates meant to protect this coastal community are still under construction. One of them, the Houma Navigation Canal, won't be complete until next hurricane season. Everyone in the area is under a mandatory evacuation notice.

In Biloxi, Miss., CBS News correspondent Mark Strassmann reports Mississippi's construction standards could place some areas in real trouble. The city faces the northeast quadrant of Isaac, potentially the storm's most powerful and punishing side.

One study by the Insurance Institute for Business Home & Safety rated construction standards in 18 hurricane-prone states, from Maine to Texas. Florida scored high, a 95 out of 100; Louisiana, 73. But Alabama scored 18, and Mississippi scored the lowest - 4 out of 100.

CBS News correspondent Rebecca Jarvis reports Isaac could lead to an increase in gas prices between 5 cents and 10 cents in the next week. More than 40 percent of U.S. refineries are along the Gulf Coast, and about half of them are directly in the storm's path.

Many refineries are either shut down or are considering whether to stop production until the storm passes, Jarvis reports. Gas supplies are already 4 percent lower than normal this year because of the closure of six other refineries earlier this month.

In Tampa, Fla., site of the Republican National Convention, CBS News chief Washington correspondent Bob Schieffer reports that GOP officials are developing response plans in case Isaac takes a turn for the worse.

"The optics of a split-screen of people in peril over here and people at a convention having fun is something they really don't want to face up to," Schieffer said on "CBS This Morning" Tuesday.

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Possibilities include canceling more sessions, which was done on Monday when the storm was near Tampa, or only having Mitt Romney address Americans after being named the party's presidential nominee, Schieffer reports.

In Washington, President Obama urged Gulf Coast residents to listen to local authorities, saying in brief remarks at the White House that "now is not the time to tempt fate.

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