Meteorology of the Dunwich Dynamo

On a Saturday closest to full moon in July thousands of cyclists congregate in London Fields and ride 200km through the night to Dunwich on the coast of Suffolk.

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Weather stats for London during the Dunwich Dynamo

Modestly described by the organisers as a “gentle bike ride to the beach, through soft country on good roads” the hours of darkness present a huge challenge for participants.

Michael Barry, the retired Canadian professional road racing cyclist, rated the challenge 5/10, harder than the 280 mile London to Paris ride which he ranked only 2/10.

Taking place in summer you would expect long hours of moonlight to be a welcome assist for these brave souls who peddle hours through the night to reach their goal. A look at the synoptic charts and statistics of each ride, however, reveals weather that is often a long way from being summery.

Looking in detail there appears to be very little chance of the ride coinciding with a heatwave. In 1999, 2003, 2004 and 2014 riders left the capital during days where the mercury reached above 80F (26.7C) – though this represents only 17% of starts. Temperatures around 70F (21.1C) are much more common.

Over 40% of the rides have seen over 1mm of rain on the opening day, this falls to 17% on the second day – a dry end to the marathon challenge is perhaps to be expected.

Patrick Field, of the London School of Cycling, said that 2007, the wettest start day to a Dynamo, was “gloriously wet”.

Perhaps what this blog also reveals is that UK weather at full moon, even in high summer, is notoriously unpredictable. Luke Howard , the father of meteorology, tried for 50 years to
prove a link between the weather and phases of the moon, but died still mystified at the ripe old age of 91.

29072007

Low pressure centred along the south coast brought a ‘gloriously wet’ Dynamo in 2007.

A movie of all synoptic charts highlights just how unsettled this time of year can be found here.

* The author is planning to take part in this year’s event to raise money for Cancer Research.

** Full stats for the weather in London during the Dunwich Dynamo back to 1992 can be found here: https://onedrive.live.com/redir?resid=A148835276FAFDEE!2561&authkey=!AEMmoeUZRVSq7uU&ithint=file%2cxlsx

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