Here is the same exercise for December ... a month which
has not exhibited a gradual warming trend over the last
four decades. It is one of the very few months of the year
when the 90s were cooler than the 80s and 70s:

Period 1961-70 1971-80 1981-90 1991-2000
CET 3.5ºC 5.4 5.0 4.7
RR(E&W) 88mm 96 101 106
SSS(E&W) 48hr 42 43 45
Icelandic Low1003mb 999 996 996
Azores High 1021 1022 1022 1022
55N05Wppp 1010.7 1010.2 1010.6 1009.6
UK Flow dirn 260º 250 240 230
UK pr gradient 7.0mb 11.2 10.2 9.9
Westerliness I 7.3mb 11.2 9.8 9.6
Southerliness I 0.5mb 2.5 2.6 3.0

So the pressure gradient and the westerliness index
(not really independent, of course) seem to correlate
with the mean temperature, while the southerliness
index seems to be less important than it was in
November. It is probably significant that winter
southerlies can range from very mild to very cold
whereas November southerlies are more often very
mild than they are very cold. The pressure at
55N 05W seems only loosely linked to mean rainfall ...
the gradually backing of the flow (southwesterlies are
probably wetter than westerlies ...?) may also be
important.

Philip Eden