Wednesday 25 December 2013

At least six dead as Atlantic Storm hits Britain and France.

At least six people have died after an Atlantic Storm hit Britain and France on Monday 23 December 2013. Simon Martindale (48) drowned in the river Rothesay in Cumbria while attempting to rescue his dog. A second, as yet unidentified, man was also killed trying to rescue a dog from the River Lemon in Devon (it should be noted that Dogs are much better swimmers than Humans, and that we should never enter waters presenting a Dog with problems, however high our regard for the animal). In Shropshire a woman was killed in a car crash during bad weather conditions. The body of an as yet unnamed woman was recovered from a river in North Wales on Monday 23 December and that of an unnamed man was recovered from a stream near Telford in Staffordshire on Tuesday Morning. A teenage boy was killed and a second severely injured when a wall collapsed at a building site in Normandy on Monday, and a Russian sailor is missing after being swept from the deck of a cargo ship in the English Channel.

A car trapped in floodwater at Brockham in Surry, England.  Tony Kershaw/Rex.

The storms also caused severe problems for transport and infrastructure in the two countries, with many people stranded or forced to cancel travel plans over the Christmas period, as flights were cancelled and road and rail networks disrupted by flooding and landslides. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. In parts if Dorset people were evacuated from their homes due to flooding, and around 300 000 homes in the UK and 250 000 homes in France were left without power.

Passengers trapped at Gatwick Airport in the UK on 24 December 2013. Sang Tan/AP.

Ocean storms form due to heating of air over the sea in tropical zones. As the air is heated the the air pressure drops and the air rises, causing new air to rush in from outside the forming storm zone. If this zone is sufficiently large, then it will be influenced by the Coriolis Effect, which loosely speaking means the winds closer to the equator will be faster than those further away, causing the storm to rotate, clockwise in the northern hemisphere and anticlockwise in the southern hemisphere.

Flooding at Dorking in Surry, England. Surry Police.

 Whilst the high winds associated these storms is extremely dangerous, the real danger from such storms is often the flooding. Each millibar drop in air pressure can lead to a 1 cm rise in sea level, and large storms can be accompanied by storm surges several meters high. This tends to be accompanied by high levels of rainfall, caused by water picked up by the storm while still at sea, which can lead to flooding, swollen rivers and landslides; which occur when waterlogged soils on hill slopes lose their cohesion and slump downwards, over whatever happens to be in their path.

Flooding at Solihull in the West Midlands, England. Birmingham Mail.

 See also At least twelve dead as Cyclone Bodil hits northern Europe, Cyclone Cleopatra kills at least eighteen people on Sardinia, At least four dead in Ridyadh floodingAround 300 believed to have died in flooding after Tropical Cyclone Three hits Somalia and Five dead and one missing as western Europe is hit by worst Atlantic Storm in a decade.

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