Forecasters say Neki has strengthened to a Category 3 hurricane far from land in Pacific, with top winds near 115 mph.
On Wednesday afternoon, Hurricane Neki was centered about 620 miles west-southwest of Honolulu and about 410 miles south of French Frigate Shoals.
A hurricane warning has been issued for part of the Papahanaumokuakea National Monument, a marine conservation area northwest of Hawaii.
Forecasters predicted Neki would probably pass wide of tiny Johnston Island. A tropical storm watch was discontinued for the island.
The uninhabited island, which is part of the isolated Johnston Atoll, is under the primary jurisdiction and control of the U.S. Air Force. The U.S. Fish and Wildlife Service has a national wildlife refuge there