Why is it so mild?

  • Why is it so mild?
    04.11.2010 16:26

    The weather has been typically autumnal across the UK over the last few days, as numerous areas of low pressure have delivered us strong winds, spells of rain and extensive banks of cloud. However, despite the very unsettled conditions, balmy south-westerly winds have ushered in some unusually mild conditions.

    Average minimum temperatures across the UK for November range from around 5 or 6 degrees Celsius across some southern areas to 3 or 4 degrees Celsius in northern parts. Across the southern half of the UK, the last few nights have been positively warm in comparison. On Wednesday night in particular, the mercury did not fall below 15 degrees Celsius in London, with 13 or 14 degrees Celsius the minimum quite widely across some southern and eastern parts.

    Not only are these temperatures significantly higher than the average minimum temperatures for October, they’re also 4 or 5 degrees above the average maximum temperature for November too. In fact, they’re higher than the minimum temperatures we’d expect in July and August.

    With such high starting points during the morning, it’s little surprise that the maximum temperatures over the last few days have been as exceptional as the overnight minima. During Wednesday, temperatures climbed to 16 degrees Celsius in London and the Home Counties, with 17 degrees Celsius recorded in parts of south-east Devon.

    By 9am on Thursday, temperatures in London had already broken 16 degrees Celsius and climbed through the afternoon to reach a high of 18.4 degrees Celsius. Even to the east of high ground across north-east Wales and north-east England, temperatures reached highs of around 17 degrees Celsius.

    The highest temperature recorded in the UK during November was 21.7 degrees Celsius at Prestatyn on the 4th November 1946, along the North Wales coast. There have been numerous occasions when 20 degrees Celsius has been reached or exceeded, all the way from HighlandScotland to the south of England.

    Clearly, temperatures on Thursday fell short of such values, and even short of the date record which, coincidentally is when the highest ever November high was recorded. However, the temperatures were impressive nonetheless.

    So what is causing the autumnal warmth and is it likely to last? Well, the first point to mention is that it’s not been quite this warm everywhere. Indeed, on Thursday, the northern half of Scotland was plagued with heavy rain and temperatures of only 6 or 7 degrees Celsius at best.

    This is because a polar air resided to the north of a warm front across northern Scotland, whilst the rest of the UK was firmly within warm, tropical air from the mid Atlantic. South-westerly winds dragged up very warm, very humid air from thousands of miles south-west of the UK, forced by numerous areas of low pressure steaming eastwards towards the UK.

    This trend is not set to last much longer, however, with colder weather likely to move in this weekend. By Sunday, maximum temperatures may struggle to top 8 or 9 degrees Celsius in southern areas as winds blow from the north, albeit light. Beyond this, a significant autumn storm looks set to hit the western side of the UK into Monday with heavy rain and severe gale force winds, possibly with some disruption to travel.

    By: Lindsay Dovey