(Updates with Bermuda official comments, NHC advisory)
By Don Burgess
HAMILTON, Bermuda, Sept 18 (Reuters) - Bermudan officials warned residents to stay off roads and prepare for possible tornadoes on Wednesday as Hurricane Humberto strengthened in approaching the Atlantic archipelago, prompting people to board up homes and businesses.
Hurricane-force winds and rains were expected to hit Bermuda by Wednesday night, the Miami-based National Hurricane Center (NHC) said, although forecasts showed the islands could be spared a direct hit.
James Dodgson, director of the Bermuda Weather Service, said conditions were already worsening and that winds could reach hurricane strength.
"I can't even rule out some isolated tornadoes... We have a very serious situation as we have a very big hurricane moving by to our north," he told a news conference.
On Wednesday afternoon, the storm's eye was located to the west of the archipelago, which lies about 650 miles (1,046 km) east of the United States.
The storm packed 120 mph (193 kph) winds and was moving at 16 mph (26 kph). It was a category three hurricane on the five-step Saffir-Simpson hurricane scale, the NHC said.
Flights have been canceled from Bermuda's main airport and some residents covered windows with wooden planks and metal sheeting in Hamilton, the capital.
National Disaster Coordinator Steve Cosham warned that the storm could topple trees and tear down power lines, while tornadoes could damage buildings.
Resident Saivo Goater placed boards across the sliding glass doors of his two-story dwelling, remembering back-to-back hurricanes in 2014 that ripped off parts of his roof.
"I don't want to go through that again," Goater said. "It's better to be safe than sorry."
Officials ended government ferry services and will close a major road leading to the airport at 6 p.m. local time. They also opened a shelter at a high school with room for 100 people.
Schools were closed and ambulances on standby, a witness said.
The Atlantic storm season has picked up pace in recent weeks.
The Bahamas is still reeling from the devastation of Hurricane Dorian, and the remnants of tropical depression Imelda have moved inland across the Gulf coast of Texas and southeastern Louisiana as it weakened, bringing warnings of flash floods and heavy rains. (Reporting by Don Burgess in Hamilton, Bermuda; Rich McKay in Atlanta; Additional reporting by Daina Beth Solomon in Mexico City; Editing by David Gregorio and Dan Grebler)
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