Hi

I thought I would spend a morning looking to see if there was any truth in the old ‘equinoctial gale’ chestnut. I know most people poo-poo the idea that gales are more frequent at periods close to the equinoxes as a popular misconception, but I thought I would try to be a bit more scientific about it, and look at the facts. The only data series that I think could help in this regard was the Lamb-Jenkinson Objective series that is maintained and made freely available by the Climatic Research Unit at the University of East Anglia. It uses a grid of mean sea level pressures across the UK to objectively obtain (amongst other indices) the Lamb Weather classification for each day of the year back to 1871. The units for the ‘Gale Day’ may well be in geostrophic ‘knots’, but I have decided to play safe and just display them as ‘units’ in my chart until someone – maybe one of my readers – can inform me differently. The units don’t really matter greatly anyway as long as the method is the applied across the whole data set.

(see http://xmetman.wordpress.com/ for graph)

As you can see from the results, the chart shows a peak in mid-January that erratically diminishes to around 50% at the beginning of June. This remains fairly flat till the second week of August when it begins to steadily increase up until the beginning of December when it flattens of a little. There is no real sign of any surge in the Gale index at the exact date of either the spring or autumn equinoxes, but there are minor peaks at around the 1st of March, and in the first week of October, that come closest to the dates of the equinoxes.

So no real sign of any equinoctial gales in either spring or autumn, just a steady decrease in the daily frequency of gales in spring, and a steady increase in autumn.

Bruce.