The first storm in a one-two punch that sent Hawaii scrambling to brace itself weakened on its approach to the state, while a second system close behind was largely expected to pass north of the islands.
The National Weather Service downgraded Iselle to a tropical storm about 50 miles before it was expected to make landfall early Friday in the southern part of Hawaii's Big Island.
Wind and rain from the system still had enough force to knock down trees, cause power outages and block roads on the Big Island, however. No deaths or major injuries were reported.
Iselle was classified as a tropical storm 11 p.m. Thursday Hawaii Standard Time when its winds slowed to 70 mph, putting it below the minimum of 74 mph for a hurricane.
The storm was weakening because of several factors, including wind shear chopping at the system and the Big Island's terrain above the water, said Chris Brenchley, meteorologist with the National Weather Service in Honolulu.
"As wind blows into the terrain, the terrain kind of redirects the wind," he said.
Nevertheless, Iselle is expected to be the first tropical storm to actually hit the state in 22 years, and another hurricane is following in its path. Hurricane Julio, a Category 3 storm, is about 1,000 miles behind in the Pacific.
Iselle, which is moving at 10 mph, was expected to pass overnight across the Big Island and then send rain and high winds to the rest of the state Friday. At midnight Friday Hawaii Standard Time, the weather service issued a flash-flood warning for the island.
The storm's predicted track had it skirting just south of the other islands, starting with Maui.
Even before its center touched land, tropical storm Iselle knocked out power on parts of the Big Island, one of the least populated islands.
"Whoop, there goes the power," 29-year-old Andrew Fujimura of Puna said as he spoke with an Associated Press reporter Thursday night. "It's fine. We'll just go to bed early tonight, I guess."
Fujimura was trading videos with a friend in Maui to help the friend see what weather conditions to expect. The videos show loud winds blowing through palm trees, white foamy waves chopping high onto shoreline shrubs and rocks — even a surfer riding rolling waves with an overcast sky on the Big Island's eastern shore.
Waves were breaking about 15 feet to 20 feet, Fujimura said.
"I can't say I'm too worried," he said. "Worst-case scenario, the power may go out a day or two. But we're prepared for that kind of stuff out here."
Emergency officials on the Big Island sent a warning to nearby residents after a geothermal plant accidentally released an unknown amount of steam containing hydrogen sulfide, a smelly, poisonous compound. Crews were working to control the release and monitor the emissions, while nearby residents were urged to evacuate if they experience discomfort, Hawaii County Mayor Billy Kenoi's office said. It was not clear whether the release was directly related to the storm.
Hundreds of people flowed into emergency shelters set up at high schools, one of which lost power. Crews worked to restore electricity to the shelter in Pahoa with at least 140 people.
Power also was lost Thursday evening in two communities on the Big Island: Waimea, a town of about 9,200 people near the island's north shore, and Puna, a district scattered with residents south of Hilo, Hawaii County Civil Defense officials said.
On Maui, power to a water treatment plant went out, prompting county officials to ask Kula residents in the middle of the island to conserve water. About 2,700 people on the island were without power late Thursday night in the town of Pukalani, about 10 miles southeast of Maui's main airport.
People prepared for the storm by making last-minute trips to the store and boarding up windows at their homes.
Meanwhile, Hurricane Julio strengthened into a Category 3 storm and followed Iselle's path with sustained maximum winds of 120 mph. Julio is projected to head just north of the islands sometime early Sunday morning.
Hawaii has been directly hit by hurricanes only three times since 1950. The last time Hawaii was hit with a hurricane or tropical storm was in 1992, when Hurricane Iniki killed six people and destroyed more than 1,400 homes in Kauai, Lau said.
Hawaii Gov. Neil Abercrombie said the state is prepared for the back-to-back storms, noting the National Guard is at the ready and state and local governments were closing offices, schools and transit services across Hawaii.
"What we're asking the people to do now is pay attention, stay focused and listen to the directions," he said.
Abercrombie said President Barack Obama had been briefed on Hurricane Iselle by federal emergency management officials.
State Attorney General David Louie promised that Saturday's primary elections, including congressional and gubernatorial races, will go forward as planned.
As residents prepared for the possible one-two punch, a 4.5-magnitude earthquake struck the Big Island but didn't cause major damage or injuries.
Travelers faced disrupted plans when at least 50 flights were canceled Thursday from several airlines, including Hawaiian Airlines, Delta, United, Air China and WestJet, the Hawaii Tourism Authority and airlines said. Some waived reservation change fees and fare differences for passengers who needed to alter their plans Thursday and Friday.
Other attractions also announced plans to stay closed for all or part of Friday, including the Royal Hawaiian Center mall in Waikiki and the Polynesian Cultural Center near Oahu's north shore.
After high winds hit Maui, California couple Rudy Cruz and Ashley Dochnahl left the island earlier than planned, getting to Oahu but failing to secure a flight back home. "We were trying to beat it, but we now will have to ride it out," Cruz said.
The storms are rare but not unexpected in El Nino years, a change in ocean temperature that affects weather around the world.
Ahead of this year's hurricane season, weather officials warned the wide swath of the Pacific Ocean that includes Hawaii could see four to seven tropical storms this year.
© Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.