Although some flooding was possible along the northern Gulf coast, the service said at 11 a.m. EDT (1500 GMT) it would issue no more public advisories on Karen.
“Karen is no longer a tropical cyclone,” the National Hurricane Center said in a statement titled “Remnants of Karen.”
The governors of Louisiana, Mississippi, Florida and Alabama had earlier declared states of emergency to speed storm preparations, and the Federal Emergency Management Agency recalled some workers who were furloughed in the federal government shutdown to assist.
But the storm’s top winds had dropped to 30 miles per hour (48 kph) Sunday morning, down from 50 mph (80 kph) on Friday.
Its remnants were expected to drop 1 to 3 inches (2.5 to 7.5 cm) of rain over portions of the central U.S. Gulf Coast and southeastern United States through Monday evening, the centre said.
Nearly two-thirds of oil output in the U.S. Gulf of Mexico was halted as Karen neared the Louisiana coast earlier this week, prompting oil and gas companies to shut platforms and evacuate workers in preparation for the storm. The Gulf accounts for about 19 percent of U.S. oil production and 6 percent of natural gas output.