Applying the indices used in the monthly analysis of flow
patterns over the British Isles on, for example,
http://www.climate-uk.com/indices/01.htm
these are overlapping 30-day means since November.
Figures are for the 30 days ending on the date given.

The mean westerly gradient for Dec21-Jan20 is
higher than for any calendar month of January, and
is close to the highest for any calendar month of
any name.

The updated period Dec 26-Jan 25 shows a
decline in westerliness and southerliness (as one
might have expected) and a jump in mean
pressure.

Period W-ly S-ly A/cyclonic
30 Nov 11.0 -1.3 18.4
05 Dec 12.3 -1.9 18.4
10 Dec 13.6 -0.3 18.2
15 Dec 12.9 1.6 19.0
20 Dec 13.7 2.7 14.4
25 Dec 16.2 1.5 11.7
30 Dec 18.2 1.1 10.8
05 Jan 21.1 1.5 10.4
10 Jan 23.9 1.2 07.6
15 Jan 24.8 1.7 06.6
20 Jan 27.0 1.5 06.1
25 Jan 23.2 0.7 10.1

Philip Eden

PS I would normally just have added this to the earlier
thread, but I get the impression that many people simply
don't see things which are posted to threads more than
48 hours old (not that I'm implying that this is "mustn't
miss" material) ... is this a fair assumption?