Will October 2020 be the wettest on record?

To answer the question let’s take a closer look at October rainfall for the whole of the UK using gridded data – which lets face it is a purely imaginary total – but seems to be all the vogue these days what with ‘global’ temperatures and the like. The wettest by a far old margin across the whole of the UK looks to have been the October of 1903 with 225.9 mm of rain which is 180% of the 1981-2010 LTA. It’s interesting to note that although seven of the wettest October have occurred this century the linear trend is flatlined for the last 157 years (1862 to 2019).

UK Gridded Rainfall Totals [mm]
October 1862-2019
Ranked UK Gridded rainfall Totals [mm]
Courtesy of the UKMO

Taking a look at the England Wales Precipitation [EWP] series that started in 1766, 1903 is still the wettest October on record but during the last 253 years there has been a small increase of 1.6% in October rainfall.

Courtesy of UKMO

Accumulations up to the 24th of October 2020

Here is a map of the percentage differences in the rainfall accumulations for the first 24 days of October 2020 from the LTA. This is a new product for me, but as far as I can see the percentage DFA’s look fairly reasonable. There are not many DFA’s less than 100% indicating a drier October than average, but there are two large clusters where rainfall accumulations are well over twice as high as the LTA for the first 24 days of the month. One of these clusters is across the northeast Scotland which has seen a rather dry 2020 up until now, the other cluster is across the southeast Midlands and the home counties around London, with Kinloss and Benson both having DFA’s of over 260% if the LTA’s I have are correct.

In Conclusion

It’s still anybody’s guess whether 2020 will break the 1903 record for the wettest October for the whole of the UK, but with still a week to go, and particularly if the weather continues in this recent unsettled mood it could be a tight run thing.

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