A one-two weather punch gained strength and churned closer to Hawaii as residents braced for the first hurricane to strike the state in more than two decades.
Hurricane Iselle strengthened and likely will maintain its speed as it passes the Big Island Thursday night, the National Weather Service said Wednesday.
On its heels, Hurricane Julio gained strength and shed its tropical storm status, becoming a second hurricane to target Hawaii.
Forecasters expect Julio to pass north of the island of Hawaii, often called the Big Island, on Sunday or Monday, National Weather Service meteorologist Anthony Reynes said
"If that happens it will be something the state of Hawaii has never seen before," Reynes said.
Terrain of the Big Island, Hawaii's largest and most eastern island, could help break up Iselle with its miles-high volcanoes, Reynes said. "The Big Island has two huge volcanoes, something that Iselle certainly will feel," Reynes said.
Still, Iselle is expected to have a severe impact across the state.
"We are gearing up for very heavy rains, possibly tropical storm force winds or worse, and strong surf," Reynes said. "We are hoping the event is on the tropical storm level, not the hurricane level."
The threatening weather disrupted travel plans, prompted flash flood warnings across the state and led to school closures.
Gov. Neil Abercrombie signed an emergency proclamation activating a state disaster fund.
The last time Hawaii was hit with a tropical storm or hurricane was in 1992, when Hurricane Iniki killed six people and destroyed more than 1,400 homes.
Julio remains too far away to predict its course, Reynes said. It could drift north and become a non-issue, he said.
National Park Service officials at the World War II Valor in the Pacific National Monument, like most Hawaii residents, were preparing for the worst.
"We're all dusting off our hurricane plans and securing the facility, loose objects, and working through what we need to do, just in case,'' says Scott Pawlowski, chief of cultural and natural resources at the Pearl Harbor monument.
On Oahu, home to Honolulu and Waikiki Beach, residents and tourists were making a run on water, canned food and other supplies — a familiar ritual for locals accustomed to the risks of living on remote islands in the Pacific.
"I have been through two hurricanes and a dock strike, and it's better to be prepared than not," David Fell of Waimanalo, a section of Honolulu, said.
"You really can't tell what's going to happen. According to local legend, hurricanes never hit the Big Island, but we'll see. It might be a first," Fell said. "If it bypasses the Big Island and tracks off Oahu, things could get pretty interesting around here really quick."
Contributing: Mike Tsukamoto in Honolulu