What a difference a year makes

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  • The high in the south blocking the low to the north, synoptic situation 15th March 2014

    Tomorrow's synoptic situation

    Last year's snow event. Red shows snow, blue shows rain, grey is rain/snow. Precipitation type radar from 22 March 2013 21:45

    An early indication for the synoptic situation for next Monday

  • What a difference a year makes
    22.03.2014 16:27

    After last week's warm weather it has been colder this weekend, as temperatures have returned to the average for March. This was caused by areas of low pressure coming in off the Atlantic and ending the stint of high pressure. The low pressure system, which arrived on Thursday, brought colder air in from the north-west which, as well as reducing temperatures, brought heavy rain to the UK.

    Tomorrow, the low currently situated above Scotland will slowly edge east. However, the north-westerly winds will remain and the UK can expect another breezy and chilly day with a mixture of sunny spells and showers. Some of the showers will be heavy in nature and produce hail and thunder at times. Northern areas are also likely to see showers turn wintry over high ground.

    In the evening there will be a brief ridge of high pressure which will create a calm, cold night, allowing temperatures to fall below zero under the clear skies bringing a widespread frost. 

    On the whole it has been a settled month compared to January and February, and rainfall totals have thankfully remained lower than average for most, with only Scotland seeing higher totals than average. This difference between the north and south has been caused by the high pressure system of last week which shielded or ‘blocked’ the southern areas from the low pressure systems spinning in off the Atlantic. However northern areas, especially Scotland were left exposed.

    It is a stark contrast to last year's March, which was also the coldest March since 1962 and the dullest since 2005. The exceptional weather was caused by an extended period of high pressure to the east or over the UK which had prevented lows from entering the UK. The blocking pattern was also responsible for keeping Europe settled, allowing temperatures to drop below average.

    In the UK an extreme snow event occurred on the 22nd and 23rd. It was particularly damaging due to the high amount of snow which fell in a short space of time. The situation occurred as a low pressure system pushed into a high that was situated to the east of the UK. The high near the UK had created a south-easterly air flow that had filtered very cold dry air in from Russia. When the warm moist air driven in off the Atlantic by the low pressure system met the cold air over UK, heavy snow was created.
    The situation continued to get worse as the high blocked the progress of the low, and with the front parallel to the winds, the heavy snow fell over some areas for a long period of time.

    The event caused power outages and transport problems as routes became buried. In Kintyre power was down for some time after two transmission pylons were toppled by ice loading.

    There are some similarities with next week’s pressure pattern, but with a lack of cold air to the east, it will be a far cry from last year .

    By: John Griffiths