"Philip Eden" philipATweatherHYPHENukDOTcom wrote:

It doesn't quite answer your question, but here are the most
westerly and southwesterly Januarys in the dataset that I use,
which goes back to 1873. The westerliness index is the difference
in sea-level pressure between 50N and 60N in the longitude of the
British Isles (i.e. 00-10W), while the southwesterly index is simply
the difference in pressure between 50N 10W and 60N 00W.

Spot the deliberate error ....

pe