Last Monday night on BBC Spotlight, David Braine was looking back at January and saying about just how windy it had been in the UK particularly the southwest. David quoted some statistics for average wind speeds for the southwest (fig 1) which got me thinking about just how windy had it been.
Because I’ve been downloading hourly SYNOP observations for the UK for quite a while now I decided to find out how many UK stations had an average mean hourly speed of 15 knots or more during each of the last four January’s, and these are the four tables for each of those months (fig 2).
As you can see from this simple method 2018 was not particularly windy across the UK in general, being overshadowed by January 2015 and 2016. The mean wind from St Mary’s on the Scilly Isles is quite a good sentinel for wind speeds in the southwest. The mean there over the last four January’s has been 20.0, 20.4, 15.4 and 19.9 knots. So I would say that at least in this small survey January 2018 was no windier than usual.
Here’s a chart of the average mean wind speed this January for stations across the southwest (fig 3). What’s puzzling is that none of those stations have a mean speed of 17 knots as David showed in his graphic (fig 1). I’m not sure how he came up with that value, unless of course its some kind of gridded regional mean wind speed from the Met Office.
The other thing I noticed that also looked a bit odd was the average gust of 27 knots that he quoted (fig 1). In a UK SYNOP report gusts are only reported if the wind speed in any hour has reached 25 knots or more. So the average would always be at least 25 knots, which would make it artificially high if it was made up of reported gusts – what about the hours when the gusts were below 25 knots? I would have thought the only meaningful statistics that you could extract would be the number of gusts that exceeded a specific threshold such as 34 knots, or the absolute highest gust for the month. Again I suppose it may be possible to derive a ‘average gust’ from a gridded dataset for a selected region. It would helpful in the future if the Meteogroup presenter on the BBC displayed a caption of where the climate statistics were for and the source of that information.