A record-breaking November

  • A record-breaking November
    07.12.2009 13:58

    November 2009 will live long in the memory of Cumbrians who experienced devastating flooding brought about by record-breaking amounts of heavy rainfall.

    In Borrowdale, the village of Seathwaite had an estimated rainfall total during November well in excess of 1000 millimetres. More bluntly, that’s one metre in a month, and getting on for half of the average rainfall aggregation of the wettest month in one of the wettest places in the world – that’s the 2,700 millimetres that Cherrapunji, India, averages in June.

    So relentless was Cumbria’s rainfall that Seathwaite established new national records for highest rainfall totals in 24 hours, 48 hours, three days, four days, five days and a week. The UK as a whole received nearly twice its average November rainfall, which made it the wettest November ever.

    The magnitude of November’s rain can be partly explained by noting the high frequency of deep, moisture-laden Atlantic depressions that tracked across or close to the British Isles. These made it the second most low-pressure-dominated month in a 136-year record, only beaten by the flood-ridden November of 2000.

    The instrumental record in the United Kingdom is the longest in the world; it is therefore extraordinary to note how many other records have been broken in just the last 15 years. These include the highest temperature, the lowest temperature, the hottest month and the greatest temperature range over 24 hours.

    The hottest day in the UK and England was 10 August 2003. A temperature of 38.5 degrees Celsius was reported at Brogdale, near Faversham in Kent, although that figure is still disputed. Even so, the next highest at London’s Heathrow airport on the same day would still be the record. Scotland’s highest-ever temperature was on the previous day: 32.9C at Greycrook, Roxburghshire but the records for Wales and Northern Ireland fell before 2004.

    The hottest month was July 2006, when the average day and night temperature across the 31 days was 17.8C, half a degree higher than the previous record in July 1983 and August 1995.

    Altnaharra in Sutherland equalled the coldest night when it dropped to -27.2C on 30 December 1995. On the same day, Altnaharra also recorded the greatest 24-hour temperature change in the UK, when milder southeasterly winds freshened to blow away intensely cold air that had been stagnating in the glens.

    The temperature even at midday was -21.2C but by 3pm it had shot up to -1.0C, an astonishing rise of 20.2C in just three hours. The temperature climbed further overnight and by the beginning of 31 December it had risen a remarkable 29.3 degrees to +2.1C.

    Because of its geography and topography, Altnaharra is no stranger to extremes. On 18 April 2003, which was Good Friday, it had a temperature range almost as high but for a different, even opposite, reason. During an early heatwave, the daytime temperature rose to 24.5C – very warm for northern Scotland in April – and fell to -3.7C overnight as cold easterly wind arrived, a change of 28.2 degrees.

    By: Stephen Davenport