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Britain enjoyed a brief respite from its downpours yesterday, but more were forecast at the end of the week in the latest episode of flooding linked to La Niña, a climate phenomenon engulfing much of the globe.Although the Environment Agency still had 73 flood warnings in place last night, water levels in rivers across Kent, Sussex, Hampshire and the Isle of Wight had started to recede. Many roads in Wales and the West Country, the Midlands and East Anglia remained closed. In Oxford, 3,000 householders were on flood alert.Flooding also caused widespread disruption on the railways. There were problems from Burstwick in East Yorkshire, where 180 properties were at risk of flooding, to Dorset. In Wilt-shire the River Avon burst its banks at Bradford-on-Avon and lorries were stranded on a causeway at Staverton.Police in Gloucestershire were hunting for two gangs of conmen who took advantage of the floods to steal from pensioners by claiming to be officials.The respite will be brief, with more rain expected today and tomorrow. The heaviest is likely to be in northern England, the Midlands and Wales.The latest flooding, and last summer’s mayhem, are both thought to be connected to La Niña, which is the less well-known opposite of El Niño.While El Niño heats the equatorial seas of the Pacific, La Niña brings a cooling off, especially towards South America. The present La Niña has led to disastrous floods in eastern Austra-lia, Indonesia, the Philippines, Mozam-bique and Zimbabwe.The West Coast of the US has also been hit by storms, bringing huge rainfalls and snowfalls. Last year for the first time, climate scientists at the Met Office discovered how La Niña could affect British weather. The key link is the jet stream, a ribbon of fast winds a few miles high that fly around the globe in big waves.“This year’s La Niña is likely to turn out to be the strongest we’ve had since 1988-89, about 1.5C (2.7F) cooler than normal. It has a big effect on global climate, temporarily cooling the globe despite global warming,” said Adam Scaife, at the Met Office. As La Niña cools the Pacific, less warm air rises off the sea, which has an impact on the atmosphere. The impact of La Niña on a global scale is like a pebble dropped in a pond; waves travel out from the source of La Niña and interact with the jet stream which affects the UK and Europe,” Dr Scaife said.The strengthened jet stream helps to develop more powerful wet and windy depressions, which it then steers across the Atlantic. A big kink in the jet stream’s path has delivered the depressions to the South West, and has hit the River Avon-a remarkable repeat of last summer’s floods.The Met Office forecast for this winter had been remarkably accurate, thanks to successfully predicting La Niña’s effects. The reason for the delay in the wetter weather during the winter was because the effects of La Niña were thought to start high up in the atmosphere and take time to work down to the surface.However, the strong jet stream alone does not explain why it has struck Britain. The other big factor is the North Atlantic Oscillation, a giant seesaw between low pressure around Iceland and high pressure over the Azores.When the Icelandic low is very deep and the Azores is very high, the jet stream drives towards Britain and northwest Europe, bringing a wet, mild winter; when the pressure seesaw slackens off, Britain has a winter of cold and snow.http://www.timesonline.co.uk/tol/news/environment/article3200801.ece
As in the days of Noah.....
