Where is the snow?

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  • Snow cover over the UK after the January snowfall 2013. Image: NASA/LANCE/MODIS

    Flooding in Chertsey, Surrey 12th January 2014. Image: Gareth Fuller (PA Wire).

    Map to illustrate low pressure pushing high pressure back towards the continent.

  • Where is the snow?
    23.01.2014 16:13

     

    A year ago this week, the UK was seeing cold and wintry weather conditions. On the 18th January 2013 a frontal system pushed north-eastwards across the UK and gave significant snowfall accumulations to southern England. Then on the 25th January 2013 another front brought snow to much of the UK, with some areas seeing more than 10cm of snow accumulation. This snow brought travel chaos to the UK with flights grounded, roads closed and trains cancelled. Throughout January 2013 temperatures were widely below the seasonal average. In East Anglia, the mean January temperature was -1.2C less than average from 1981 to 2010.

    In comparison, this winter has been exceptionally mild and wet. December saw mean temperatures ranging between 0.8C and 2.5C above the seasonal norm, and January has continued the trend with temperatures up until the 15th January remaining at least 1C above the seasonal average. This also corresponds with overnight average temperatures which again have been at least 1C above the norm. 

    Most areas had 100% of their mean rainfall totals in December and some areas, such as south-east England saw 150% of their average rainfall. In addition to this in January, by the 15th, all of the UK had seen at least 100% of its normal January rainfall totals and in some parts, such as north Scotland, north-west England and Wales 150% of the average was seen. This led to widespread flooding across the UK, particularly over the Christmas period. In addition to this, the heaviest rainfall often coincided with strong wind gusts and high tides, increasing the risk of flooding in coastal areas. 

    The main reason for this abnormally mild and wet winter has been the south-westerly to westerly flow which has continued to influence the UK. With the current positioning of the jet stream, low pressure systems have continually been flung towards the UK, many of which deepened as they approached the British Isles. As the winds around a low pressure system travel anti-clockwise these systems have brought in mild Atlantic conditions in from a south-westerly direction.

    Normally at some point during the British winter an easterly wind will affect the UK bringing colder conditions from the continent. This is usually due to high pressure over the continent strengthening and pushing the low pressure systems out the way. However, this winter, the low pressure systems have continually pushed the high pressure out the way (see map). The other perfect snow conditions for the UK can be found in our previous article.

    At the moment, the UK looks sets to remain unsettled with further showers or longer spells of rain affecting it. However, there are some hints of colder conditions moving in towards the end of the month increasing the risk of snow.

    By: Sally Webb