Tropical Storm Iselle battered Hawaii with driving winds and rising surf on Friday, knocking down trees and causing power outages, the first of two major storms due to hit the archipelago as the more powerful Hurricane Julio gathered steam behind it.
More than 1200 people flocked to evacuation shelters across the Big Island, according to County of Hawaii Civil Defense, as heavy rains and strong winds pummelled areas of East Hawaii from the Puna area to the town of Hilo.
Hawaii Electric Light Company had about 5000 customers without power, mostly in East Hawaii, a Hawaii County official said.
With its eye still about 80 km south of Hilo, on the Big island, Iselle had weakened from a hurricane to a tropical storm, packing maximum sustained winds near 110 kph, with higher gusts, the US Central Pacific Hurricane Center.
The storm could still bring waves of up to 8 metres on southeast-facing shores on the Big Island over the next few hours before passing south of the state's smaller islands, Central Pacific Hurricane Center meteorologist Tom Evans said.
''With a few hours before the centre making landfall we can still see that high surf on the southeast-facing shore of the Big Island,'' Evans said.
Farther east, Hurricane Julio had gained momentum and was expected to pass just north of Hawaii by late Monday.
That hurricane was upgraded late to a Category 3 storm, with maximum sustained winds increasing to near 195 kph, the National Hurricane Center said.
It was moving west-northwest at 26 kph and was expected to weaken on Saturday.
In anticipation of the rare back-to-back storms, Hawaii residents scrambled to stock up on supplies as state officials warned of the potential for flash floods, mudslides and power outages in the normally calm tourist haven.
Governor Neil Abercrombie signed an emergency proclamation freeing up funds and resources and authorities advised residents to prepare seven-day disaster supply kits and cautioned them against driving except in an emergency.
''Everybody knows that a real rough time is coming,'' Abercrombie told a news conference.
Hawaii's schools would be closed on Friday, but authorities planned to keep airports open so planes could land in an emergency although some airlines had cancelled flights, officials said.
Several shopping malls on Oahu would also be closed.
Malia Baron, an Oahu resident visiting the Big Island, known for its volcanoes, black-sand beaches and coffee farms, reported the weather as.
''Our power is out again. It's been on and off all evening and we were lucky enough to finish cooking before one of the longer outages,'' she said.
Power was out at the Olinda Water Treatment plant in a rural area of Maui, and officials told some 700 water customers to conserve water, County of Maui spokesman Rod Antone said.
Emergency officials also told residents in the area of the Puna Geothermal Venture plant in Pohoiki to stay indoors or evacuate to safe zones after a spill of poisonous hydrogen sulphide.
It was not immediately clear how serious the spill was.
Preparations for a primary election scheduled for Saturday continued, officials said, but added they would reassess how to proceed on Friday after Iselle hits.
On the Big Island, a downpour soaked customers who dashed from cars to the Sunshine True Value Hardware store in Kapaau only to discover shelves already picked clean of batteries, flashlights, duct tape and plywood.
Sales clerk Caryl Lindamood tried to stay cheerful.
''Mother Nature sure does like to stir things up for us, doesn't she?'' she said, joking about both the storms and a small 4.5 magnitude earthquake that struck the Big Island 19 km west of Waimea hours before.
Kailua-Kona resident Lisa Hummel, 44, said her family was filling water containers and stocking up on batteries, candles and flashlights, and planned to shelter in their basement when the hurricane arrives.
''We'll probably make a pot of chili and ride it out,'' she said.