HONOLULUHONOLULU (Reuters) - Hurricane Lane churned slowly toward Hawaii late on Wednesday as schools, government offices and business closed and residents stocked up on supplies and boarded up homes.

A direct hit could bring the U.S. Pacific island state's worst storm in a quarter century, forecasters said.

Lane packed sustained winds of up to 145 miles per hour (230 km/h) and could dump as much as 20 inches of rain that could trigger flash floods and landslides, the National Weather Service said.

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"Preparations to protect life and property should be rushed to completion," the service added. "Life threatening impacts are likely in some areas as the hurricane makes its closest approach."

Lane - classified as a powerful Category 4 storm on the five-step Saffir-Simpson scale of hurricane strength - was expected to hit the Big Island overnight and slam the island of Maui on Thursday, according to the service.

To the north, Oahu was under a hurricane warning while Kauai remained on hurricane watch meaning it could face similar conditions starting Friday morning.

Governor David Ige urged residents to prepare for the worst by setting aside a 14-day supply of water, food and medicines.

"I urge our residents and visitors to take this threat seriously and prepare for a significant impact," the governor said at a news conference in the state capital, Honolulu.

He also announced that all public schools, University of Hawaii campuses and non-essential government offices on the islands of Oahu and Kauai would be closed for at least two days starting on Thursday.

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STORE SHELVES STRIPPED

The shelves of a downtown Honolulu Walmart were stripped of items ranging from canned tuna to dog food. Shoppers jostled with one another to get the last boxes of ramen noodles.

"There's nothing in there," said one shopper leaving the store.

City residents used carts to push cases of bottled water and coolers full of ice, after warnings of possible power outages and evacuations.

Cars waited in long lines at gasoline stations in Honolulu and people could be seen pulling small boats from the water ahead of Lane's expected storm surge.

"I went to Safeway last night for regular groceries, everyone was in a panic," said Thao Nguyen, 35, an employee at a Honolulu branch of Hawaiian shirt retailer Roberta Oaks.

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"People were buying cases of tiny water bottles."

U.S. President Donald Trump directed FEMA and administration officials to remain in close coordination with the state, White House spokeswoman Sarah Sanders told reporters.

"The president is deeply concerned for the well-being of all Hawaiians," she said.

U.S. Navy ships and submarines based in Hawaii were instructed to leave port, a common practice as a hurricane approaches to avoid damage.

As of 11 p.m. (0900 GMT Thursday), the storm was centered 235 miles (380 km) south-southwest of Kailua-Kona, the weather service said.

The outer bands of the storm were already dumping 1 to 3 inches an hour of rain on parts of the Big Island as the eastern side of the island was under a flash flood warning, said Gavin Shigesato, a NWS meteorologist said.

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The most powerful storm on record to hit Hawaii was Hurricane Iniki, a Category 4 storm that made landfall on Kauai island on Sept. 11, 1992, according to the National Oceanic and Atmospheric Administration. It killed six people and damaged or destroyed more than 14,000 homes.

(Additional reporting by Gina Cherelus in New York, Brendan O'Brien in Milwaukee and Steve Gorman and Dan Whitcomb in Los Angeles; Writing by Andrew Hay; Editing by Tom Brown, Sandra Maler and Andrew Heavens)