Honolulu - The first storm in a one-two punch heading for Hawaii was rapidly weakening on its approach to the state, while a second system close behind it strengthened and was on track to pass north of the islands.
The National Weather Service downgraded Iselle to a tropical storm about 80km before it was expected to make landfall early on Friday in the southern part of Hawaii's Big Island. By 14:00 Hawaii Standard Time on Friday, the storm was swirling about 6km from the Kau coastline.
Wind and rain from the system still had enough force to knock down trees, cause power outages and block roads on the Big Island. No deaths or major injuries were reported. The storm is expected to inundate Hawaii with up to 200mm of rain.
Maui County spokesperson Ryan Piros said outside it was raining and the wind was cranking, but in the overnight hours he was listening to a largely quiet police scanner.
Iselle was classified as a tropical storm at 23:00 HST on Thursday. By early Friday morning its winds had slowed to 100km/h, well below the 120km/h threshold 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 hit the state in 22 years, and another hurricane is following in its path. Hurricane Julio, a Category 3 storm, is about 1 600km behind in the Pacific.
Iselle, which is moving at 6km/h, was expected to pass overnight across the Big Island and then send rain and high winds to the rest of the state on Friday. At midnight on 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 centre touched land, Tropical Storm Iselle knocked out power on parts of the Big Island, one of the least populated islands.
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 on 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 Defence officials said.
Meanwhile, Hurricane Julio strengthened into a Category 3 storm and followed Iselle's path with sustained maximum winds of 195km/h. Julio is projected to head just north of the islands sometime early on 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 Governor 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.
Abercrombie said President Barack Obama had been briefed on Iselle by federal emergency management officials.
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.
Travellers faced disrupted plans when at least 50 flights were cancelled on 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.
The storms are rare but not unexpected in El Nino years, a change in ocean temperature that affects weather around the world.