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Nate strengthens to hurricane as it bears down on northern Gulf Coast, New Orleans

(This article was last updated at 11:00 a.m. Saturday based on the latest National Hurricane Center advisory.)

Intensifying Hurricane Nate is closing in on the northern U.S. Gulf Coast. Southeast Louisiana, including vulnerable New Orleans, lies in the path – although the worst conditions may end up just to its east in coastal Mississippi and Alabama.

Nate should make landfall between late Saturday night or early Sunday morning. Damaging winds, gusting over 100 mph, and flooding threaten the region from roughly Morgan City, La., to Pensacola, Fla. Louisiana, Mississippi, Alabama and Florida have all declared a state of emergency ahead of the storm.

Along the coast, near and just to the east of where the storm center moves ashore, a storm surge or rise in ocean water of up to 7 to 11 feet above normally dry land is expected, which could inundate homes, businesses, and roads. “Life-threatening storm surge flooding is likely along portions of the northern Gulf Coast, and a storm surge warning has been issued from Morgan City, Louisiana, to the Okaloosa/Walton county line in Florida,” the National Hurricane Center said.

The Hurricane Center has issued hurricane warnings for southeastern Louisiana and coastal Mississippi and Alabama, including New Orleans, Biloxi and Mobile. Rainbands and tropical-storm force winds could begin there as soon as Saturday afternoon.

“[P]reparations to protect life and property should be rushed to completion in these areas,” the Hurricane Center said.

Over the warm waters of the Caribbean, Nate strengthened and became much better-organized Friday before moving into the southern Gulf of Mexico overnight, when it was classified a hurricane. At 11 a.m. Saturday, it packed 90 mph maximum winds while centered 180 miles south-southeast of the mouth of the Mississippi River. The storm is racing to the north-northwest at 22 mph.

The storm could gain a little more strength as it traverses the warm waters of the central Gulf before slamming into the U.S. Gulf Coast on Saturday night or early Sunday.

The official National Hurricane Center forecast is for the storm to make landfall as a Category 2 hurricane with winds of 105 mph.

The majority of model simulations have converged on landfall between Southeast Louisiana and the Alabama-Florida border. Of course, exactly where in this zone the storm comes ashore is important, as the core of strongest winds is likely to be fairly small and the storm’s most severe hazards will tend to occur near and just to the east of where it makes landfall. Coastal Mississippi and Alabama have the highest likelihood of a direct hit.

Hurricane-force winds extend just 35 miles from the center, mostly on the east side of the storm. Tropical storm-force winds expand outward about 125 miles, again mostly on the east side of the storm.

New Orleans in focus

Around New Orleans, while some flooding from rainfall is a possibility, the main concerns are storm surge and damaging winds.

If the storm makes landfall just west of the city, it could push a surge of 5 to 8 feet above normally dry land, causing significant inundation. Landfall east of the city, which is most likely, would reduce the surge potential some.

In a worst-case surge scenario, the National Weather Service warns that “large areas of deep inundation” could occur, causing “structural damage to buildings, with several washing away.” It also said roads could be washed out with “major damage to marinas, docks, boardwalks and piers.”

Links: Detailed local impact statements from the National Weather Service for Lake Charles, La. | New Orleans | Mobile-Pensacola

Winds are likely to gust over tropical storm-force, which could cause downed trees, minor structural damage, and power outages.

Two to four inches of rain are possible in New Orleans, enough to cause localized flooding, the Weather Service said. Because Nate will move through the region relatively quickly, it will limit the potential for more serious rainfall. The Advocate, a news organization serving New Orleans, wrote that several of the city’s pumping stations, which help dislodge floodwaters, are not at full capacity, which could cause problems if rainfall is at the high end of projections.

The broader Gulf Coast and eastern United States

The last time this part of the coastline experienced a hurricane landfall was Category 1 Hurricane Isaac in late August 2012, and Nate should produce similar impacts.

Because the worst weather is expected near and just east of the storm center, areas east of New Orleans, including Biloxi, Mobile and Pensacola, are more likely to experience serious impacts, including damaging wind gusts, a storm surge of several feet and at least several inches of rain.

After Nate crosses the coast, it is likely to carry gusty winds and a serious swath of heavy rainfall to the north and northeast between Sunday and early next week. The Southern Appalachians, in particular, may face a flash flooding risk Sunday and Monday — as at least 3 to 6 inches of rain could fall in a short time.

The storm has been blamed for at least 22 deaths in Nicaragua and Costa Rica, mainly from flash flooding.