Hurricane Isaac raked the Louisiana coast and headed for a shuttered New Orleans late Tuesday, with brutal timing that made up for much of what it lacked in punch.

Just hours shy of the seventh anniversary of Hurricane Katrina, Isaac's approach left deserted streets from the city'sfamous French Quarter to Tampa, Fla., about 775 kilometres away, where Republican conventioneers pressed on with only a passing mention of the storm's arrival.

A Category 1 hurricane with winds at about 130 km/h Isaac came ashore at 6:45 p.m. CT near the mouth of the Mississippi River in southeastern Louisiana, drenching a sparsely populated neck of land that stretches into the Gulf of Mexico. But the worst was still to come as it zeroed in on New Orleans, 120 kilometres to the northwest.

At midnight Tuesday, the hurricane had slowed to a forward speed of 10 km/h. It was forecast to slow even further over the next day or two as it drifts over the southeastern coast of Louisiana before heading inland, according to an advisory from the U.S. National Hurricane Centre in Miami.

While much less powerful than Katrina in 2005, Isaac unleashed fierce winds and soaking rains that knocked out power to more than 100,000 homes and businesses.

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.

While many residents stayed put, evacuations were ordered in low-lying areas of Louisiana and Mississippi, where officials closed 12 shorefront casinos.

One of the main concerns along the shoreline was storm surge, which occurs when hurricane winds raise sea levels off the coast, causing flooding on land. A storm surge of 3.1 metres was reported at Shell Beach, Louisiana late Tuesday while a surge of two metres was reported in Waveland, Mississippi, the Hurricane Center said.

Ed Rappaport, the centeres deputy director, said Isaac's core would pass west of New Orleans with winds close to 130 km/h and head for Baton Rouge.

"On this course, the hurricane will gradually weaken," Rappaport said. He said gusts could reach about 160 km/h 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 the 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 neighbourhood by Katrina's floodwaters, yet chose to stay put this time. "It's a special name that means `God will protect us.'"

Officials, chastened by memories and experience, advised caution.

"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.

Roads, bridges, the port and airport are closed, and some 100,000 people are without power. Curfews are in effect for some areas.

"The expectation is … that most people within this vicinity will lose power at some point in the next 48 hours," the CBC's Adrienne Arsenault reported from New Orleans.

Residents were ordered out of low-lying areas in Louisiana and Mississippi. At least one tornado spun off of Isaac in Alabama. There were no immediate reports of damage or injuries.

'I know how to survive'

At businesses near the French Quarter, windows were boarded up and sandbags were stacked a few feet high in front of doors.

Dozens dead in Haiti

At least 24 people are dead in Haiti following its brush with Isaac over the weekend, say authorities. Three others are still missing.

The Caribbean nation was hardest hit in its southern region, which saw heavy flooding. Another five people died in the neighbouring Dominican Republic, bringing the storm's current death toll to 29.

Some tourists said they would ride out the storm near the city's famed Bourbon Street, and there was little to suggest a sense of worry.

At a Hyatt hotel in the French Quarter, Nazareth Joseph braced for a busy week and fat overtime paycheques. Joseph said he was trapped in the city for several days after Katrina and helped neighbours escape the floodwaters.

"We made it through Katrina, we can definitely make it through this. It's going to take a lot more to run me, I know how to survive," he said.

Republicans cut one day off their presidential nominating convention in Tampa, though in the end it bypassed the bayside city. Isaac is also testing elected officials along the Gulf from governors on down to show they're prepared for an emergency response.

President Barack Obama said Gulf Coast residents should listen to local authorities and follow their directions as Isaac Storm approached. "Now is not the time to tempt fate. Now is not the time to dismiss official warnings. You need to take this seriously," Obama said.

Levees rebuilt

New Orleans is in much better shape than it was before Katrina with an injection of about $14 billion in federal funds to fix damage done by Katrina and upgrade the system.

The Army Corps of Engineers has spent the last seven years working nearly around the clock to raise levees several metres, install new stronger floodwalls at critical places and strengthen almost every section of the 209-kilometre perimeter that protects the greater New Orleans area.

The system is built to hold out storm surge of about 9 metres where the city's boundaries meet the swamps and lakes near the Gulf of Mexico.

The improvements include several massive floodgates that are shut when a storm approaches. In particular, a new surge barrier and gate that closes off the Inner Harbor Navigation Canal near the Lower 9th Ward has reduced the risk of flooding in an area long viewed as the city's Achilles heel.

Still, there could be problems, especially if Isaac dumps lots of rain on the city.

"I don't really trust the levees," said Robert Washington, who planned to evacuate along with his wife and five children. "I don't want to take that chance. I saw how it looked after Katrina back here."

One question haunting locals is how much oil left over from the Gulf oil spill in 2010 might wind up on the beaches because of Isaac. Experts believe large tar mats lie submerged just off the coast, but no one knows where they are or how many might be in the Gulf.

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Stacey Davis, left, and his son board up windows on their home before tropical storm Isaac hits Tuesday in New Orleans. (David J. Phillip/Associated Press)