Within the North Atlantic ocean , tropical or subtropical cyclones are named by the National Hurricane Center ( NHC ) when they are judged to have intensified into a tropical storm with winds of at least 65 km\/h , ( 40 mph ) . Within the North Atlantic ocean , tropical or subtropical cyclones are named by the National Hurricane Center ( NHC\/RSMC Miami ) when they are judged to have intensified into a tropical storm with winds of at least 65 km\/h , ( 40 mph ) .