Ireland has closed schools and hospitals and warned people to stay indoors as tropical storm Ophelia threatens to lash the country with the worst weather in 50 years.
The armed forces have been dispatched to bolster flood defences in some areas as the weather service warned of flash flooding and damage to buildings from winds gusts over 130 kilometres per hour.
Hurricane force winds are expected in every part of the country, the government warned. Tropical-storm force winds may also be seen in Wales and the north and west of England, the US government's National Hurricane Centre said.
"Our concern is to avoid a situation where we have fatalities as a result of the extremely destructive and violent gusts that we are expecting," the chairman of Ireland's National Emergency Coordination Group Sean Hogan told state broadcaster RTE.
"All non-essential activity should be deferred. Do not be out tomorrow in this storm," Hogan said.
Britain's meteorological service says the storm poses a danger to life and is likely to cause transport cancellations, power cuts and flying debris.
British media are comparing the storm to the Great Storm of 1987, which subjected parts of the United Kingdom to hurricane strength winds 30 years ago to the day.
The centre of Tropical Storm Ophelia, the sixth major hurricane of the Atlantic season before it was downgraded to a tropical storm overnight, was around 300 kilometres south of Ireland at 0500 GMT (4 pm AEDT) on Monday, the Irish weather service said.
It was expected to make landfall at around 0900 GMT (8 pm AEDT), it said.
The government says the storm is likely to be the worst since Hurricane Debbie, which killed 12 in Ireland in 1961.
