NEW ORLEANS—Weather forecasters warned residents along the northern Gulf of Mexico coast to rush preparations Saturday in anticipation of an intensifying Hurricane Ida, which is expected to bring winds as high as 130 mph, life-threatening storm surge, and flooding rain when it slams ashore in Louisiana on Sunday. Highways on the northern Gulf Coast saw steady traffic as people moved to get out of the storm’s way. Trucks pulling saltwater fishing boats and campers were part of a steady stream of vehicles leaving the coast on Interstate 65 in south Alabama. Traffic snarls were reported on Interstate 10 heading west out of New Orleans. Ida, a tropical depression two days earlier, was strengthening so quickly that New Orleans officials said there was no time to organize a mandatory evacuation of the city’s 390,000 residents, a task that means coordinating with the state and neighboring locales so that inbound lanes on …