Friday, September 14th 2012, 3:08 AM EDT
#The Met Office claim to have developed a far better way of predicting cold snaps weeks in advance
#Forecasters have developed a computer program which tracks changes in the atmosphere thought to be key to extreme cold spells
The Met Office was criticised over inaccurate forecasts ahead of the Big Freeze winter two years ago.
However, it now claims it is far better at predicting cold snaps weeks in advance.
Forecasters have come up with a computer program which can track changes high up in the atmosphere, which are thought to be key to extreme cold spells.
This ‘high top’ system includes weather patterns called sudden stratospheric warmings – SSWs – which block warm air flowing across the Atlantic to Northern Europe and cause temperatures to plunge.
It was found in a study by Met Office climate experts to perform better than the model used at the time and would have predicted the weather chaos with more certainty.
When the new system was used the following winter, it was able to predict freezing temperatures two months in advance, it said.
Forecasters insist they did warn about low temperatures in 2009-10 when the coldest winter for a century saw Britain blanketed in snow and the mercury plunge to minus 17.6C (0.3F).
They installed the new model in late 2010, and tested it retrospectively for predicting weather from the previous October to February in a study published in Environmental Research Letters. Co-author Jeff Knight said by October 2010 the high top version of their computing system – named GloSea4 – was ‘indicating an increased chance of a cold start to winter’.
He said: ‘That year December was the second coldest in 350 years. It also highlighted the possibility that conditions in late winter were likely to be less harsh, which was indeed the case.
‘In 2011, GloSea4 predicted that a mild, westerly winter was likely. This turned out to be the case – only the first two weeks of February 2012 were cold.’
Ninety-day forecasts for the public were ditched in 2009 after a predicted ‘barbecue summer’ turned out to be a washout. The public can see a 30-day forecast and seasonal forecasts are only given to government and businesses.
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