The storm, with sustained winds of 40 miles (65 kilometers) per hour, was tracking north at about 10 mph some 155 miles south of the port of Morgan City, Louisiana, shortly before 8 a.m. New York time, the National Hurricane Center said in an advisory.
Karen’s approach forced the shutdown of some Gulf oil and natural gas operations. Forecasters earlier ended a hurricane watch for parts of the Gulf Coast, saying the storm was less likely to strengthen. Even so, heavy rains, gusty winds and flooding threaten the southeastern U.S. this weekend.
“On the forecast track, the center of Karen is anticipated to be near the coast in the tropical storm warning area tonight or Sunday morning,” the center said.
Karen was disrupted after encountering dry air, while high shear -- when winds blow at varying speeds or directions at different altitudes -- blew the biggest thunderstorms away from the center, breaking up its structure, forecasters said.
The system’s strength is forecast to be little changed over the next two days. A tropical storm warning was in place from Morgan City to the mouth of the Pearl River on the Louisiana-Mississippi line, while a storm watch was in effect for New Orleans, Lake Maurepas and Lake Pontchartrain and from east of the Pearl to Indian Pass in the Florida panhandle.
The official track has Karen clipping the extreme southeastern tip of Louisiana and then going ashore near Mobile, Alabama, and Pensacola tomorrow. The system may drive tides as much as 4 feet (1.2 meters) higher than normal from Terrebonne Bay in the Mississippi delta to Tampa Bay, Florida.
“The combination of storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters,” Jack Beven, a hurricane specialist at the center, wrote in an advisory.
Karen is the 11th named storm of the Atlantic hurricane season, which began June 1 and ends Nov. 30. The system would be the second to hit the U.S. this year. Tropical Storm Andrea made landfall in northwestern Florida in June and then moved up the East Coast.
About 39 percent of natural-gas production and almost half of Gulf oil output was closed due to the storm, the U.S. Bureau of Safety and Environmental Enforcement said yesterday. In all, 185 platforms and 18 rigs were evacuated, accounting for 693,345 barrels a day of oil and about 1.5 billion cubic feet of gas.
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