Sunday 24 January 2021

Hundreds of homes flooded as Atlantic Storm Christoph sweeps across England and Wales.

Hundreds of homes have been flooded after Atlantic Storm Christoph swept across England and Wales on Wednesday 20-Thursday 21 January 2021. In Wales the worst flooding occurred around Neath Port Talbot, Ruthin, and Bangor on Dee, with hundreds of homes evacuated in Neath due rising floodwaters. In England the worst of the flooding occured in Cheshire, Mersyside and Greater Manchester, with several Cheshire villages evacuated due to flooding.

 
A flooded home in the village of Lymm in Cheshire, following the passage of Atlantic Storm Christoph. PA Media.

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 in Welney on the Norfolk/Cambridgeshire border following the passage of Atlantic Storm Christoph. Geoff Robinson/The Guardian.

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.

 
Evacuations being carried out in the village of Northwich in Cheshire. Cheshire Police/PA Media.

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