Wettest Day on Record
by Kirsty McCabe, FRMetS
Heavy rain and autumn gales will sweep across the UK this weekend, marking almost a year since the UK experienced its wettest day on record, when enough rainfall fell to fill Loch Ness!
On Saturday 3rd October 2020, a large number of weather stations recorded their wettest October day on record, including several with 100+ year records. The stations were scattered right across the UK, from London to the West Midlands to Lancashire to Aberdeenshire. Enough rain fell in a single day to fill Loch Ness. To put that into context, as well as the mythical Nessie, Loch Ness contains more water (7,452 million cubic metres) than all the English and Welsh lakes together.
It is highly unusual for rainfall totals as high as this to be recorded on the same day across such a large swathe of the country. The average rainfall across the entire UK was 31.7 mm, beating the previous record of 29.8 mm set on 25th August 1986. The Met Office’s Mike Kendon and Mark McCarthy, head of the Met Office National Climate Information Centre, take a closer look at the rainfall series in a study published in the Royal Meteorological Society’s Weather journal.
The intense rainfall of Saturday 3rd October 2020 followed a dry September, so the impacts from flooding were thankfully not too severe for the UK. Mike and Mark note that of the top 100 wettest days in the UK daily series from 1891, 24 have occurred since the year 2000. A study to evaluate long-term trends in the annual maximum series, to determine any change in likelihood of an event such as the rainfall of 3 October 2020 under human-induced climate change, has not yet been conducted.
However, in general terms, a warmer atmosphere holds more water vapour and, under a warming climate, autumn and winter rainfall over the UK is likely to increase, with individual rainfall events becoming more intense. So, the question as to whether this record will be broken again must remain ‘when’ and not ‘if’.