(AP) - 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 New Orleans' famous French Quarter to Tampa 480 miles away, where Republican conventioneers pressed on with only a passing mention of the storm's arrival.

A Category 1 hurricane with winds at 80 mph, Isaac came ashore at 6:45 p.m. CDT 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 the slow-moving storm zeroed in on New Orleans, roughly 75 miles to the northwest.

While much less powerful than Katrina in 2005, Isaac unleashed fierce winds and soaking rains that knocked out power to more than 200,000 homes and businesses.

The storm drew intense scrutiny because of its timing - just before the anniversary of the hurricane that devastated New Orleans, 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.

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," Rappaport said Tuesday night from the Miami-based center. He said gusts could reach about 100 mph at times, especially at higher elevations 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.

Tens of thousands of people were told to leave low-lying areas, including 700 patients of Louisiana nursing homes, but officials decided not to call for mass evacuations like those that preceded Katrina, which packed 135 mph winds in 2005.

Isaac also promised to test a New Orleans levee system bolstered after the catastrophic failures during Hurricane Katrina. But in a city that has already weathered Hurricane Gustav in 2008, calm prevailed.