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Weather Watch: How cold snap in USA has played part in UK flooding

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  • by Daniel Adamson, head of meteorological research and development at MetDesk in Wendover
 

With just over two weeks remaining of the ‘meteorological’ winter season (December to February), rain, winds and floods have undoubtedly been the story of winter 2013-14.

December and January combined was the second wettest two-month period across England and Wales in a rainfall series dating back to 1766, whilst southern England had its wettest January on record and there have only been a handful of dry days in the past 8 weeks.

Here in Bucks, over 200% of the average January rainfall fell last month, which means our county had some of the biggest excesses compared to normal, despite the flooding headlines being dominated by the West Country and west Wales.

In contrast, the USA has been experiencing a bitterly cold, snowy winter, and perhaps we can pin some of the blame for our own ‘weather woes’ on this.

The unusually cold air over North America this winter has resulted in greater than normal temperature gradients across their side of the Atlantic, with much warmer air above the ocean to the south-east of the eastern US states.

These gradients largely determine the strength and position of the polar ‘jet stream’ – a narrow band of very strong, typically westerly, winds 5-7 miles above the Earth.

This winter, there has been an unusually strong polar jet, generating a frequent train of deep low pressure areas passing across our shores.

You’ve guessed it, low pressure equals lots of wind and rain!

Furthermore, the position of the jet stream in recent weeks has driven the low centres and resulting heaviest rain and gales across the heart of the UK, rather than north-west Scotland, which is the climatological norm. Indeed, January was actually around 50% drier than average in the north-west Highlands!

So when will the current set-up change? Well, not yet!

The forecast continues to be dominated by low pressure, with heavy rain and strong winds today, showers tomorrow and more rain on Friday. A bright, breezy start to the weekend but then further rain later on Sunday!

>@metdesk

>www.metdesk.com

>MetDesk’s brilliant new weather app, Home and Dry, great for tracking UK storms and heavy rainful, is now available to download from the Apple store

 

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