Torrential downpours and gales are forecast to sweep in from the Atlantic and drench large parts of Britain this weekend.

Two wide bands of rain are expected to hit the South West of England and Wales particularly hard, with winds rising to gale-force in the Bristol Channel and English Channel.

Such meteorological turbulence is not unknown in mid-autumn, but what makes the weather patterns particularly interesting is that they carry the remains of a tropical storm that has boomeranged across the Atlantic.

Several days ago Tropical Storm Laura brewed up far off the eastern coast of the United States. As the storm drove farther north it was expected to run out of steam over the colder seas and eventually fizzle out. But Laura unexpectedly found a new lease of life off the coast of Newfoundland, turning into a tropical cyclone.

Although there was never any danger of the storm hitting land, it was caught by the high-altitude jet stream winds and sharply turned right towards Britain.

As Laura sped over even colder waters, it lost the warm temperatures needed to power its huge energy demands and dropped from tropical storm status. It was then sucked into an Atlantic depression travelling eastwards, and disappeared off the hurricane warning maps.

The remains of Laura live on, though. Its rich cargo of hot, humid tropical air gave a big kick to the Atlantic depression, clashing with its mass of cold air and setting off something much more powerful. The results are what Britain will see in today’s winds and rain.

With another soaking forecast for tomorrow, an accumulated 50mm (2in) or more rain could saturate the ground and cause flooding, especially in southwest England and Wales.

The Met Office is also advising people in the North West and Midlands to prepare for up to 30mm of rain, although the Environment Agency has not issued any flood warnings for the weekend.

This has been a particularly savage year for hurricanes, with Hurricane Ike causing extensive damage in the United States. Several weeks remain in the hurricane season, however, and forecasters are expecting further serious storms to develop.

Poor forecasts for Britain — with more wind and rain expected over the next week or two — could worsen if any of these become turbo-charged by former tropical storms.

This is the time of year when Britain is most likely to be battered by the remains of tropical storms and hurricanes that get wrapped up in Atlantic gales, sometimes with devastating effects. In 1961 the former Hurricane Debbie battered Ireland, with winds gusting to more than 100mph, causing 17 deaths. In 1966 the former Hurricane Faith killed four people in Scotland.

Worst of all, however, may have been 1588, when the Spanish Armada fled down the West Coast of Scotland and Ireland trying to get back to Spain. Much of the fleet was wrecked in storms that are believed to have been charged up by old hurricanes.

Barry Grommet, a Met Office meteorologist, said that the worst area for rain on Saturday was likely to be the North West of England, with the weather hitting farther south tomorrow.

“Generally around the country the rainfall will be about 10 to 15mm, but the most extreme amount will be 30mm, which is likely to be seen in the North West, the Midlands and East Anglia.

“Saturday will be quite windy too. We’ll see gales around coastal areas of around 30 to 40mph, not too extreme but certainly a bit of a stormy feel throughout the weekend.”

Mr Grommet said that the wet, windy weather was likely to continue into next week, but that temperatures in London on Monday would be surprisingly warm.