Interesting thoughts for January and February....
Most of the models are pointing towards a winter with an above average incidence of blocking to the north and east of Britain, particularly over Scandinavia and Russia. However, there is also some support for an enhanced westerly flow with low pressure in charge, including the Met Office seasonal forecast ensemble. Note that the models that go for a westerly winter still do not have particularly warm conditions over the British Isles, with the cold anomaly in the North Atlantic perhaps making its presence felt as per winter 2014/15.
In general the signal for westerly dominated conditions is strongest for December, but the current model outputs are suggesting a blocked start to December with frequent northerly and north-westerly winds. Thus we will probably see a change to more unsettled conditions as December progresses, though still with potential for further cold shots mainly for the north, most likely from the north and north-west rather than east, especially with the Madden-Julian Oscillation heading towards phases 7 and 8 which are correlated with blocking to the north and north-west of the UK.
For January we have much stronger support for eastern blocking and potential for some easterly incursions, and a continued suggestion of relatively cyclonic conditions. In that kind of setup we have to bear in mind that the UK often lies “at the end of the line” for easterlies and so sometimes we see very cold air masses accumulate over central and eastern Europe that never make it as far west as the British Isles.
For February the signal is weaker but this month is the most likely of the three to have anticyclonic spells, which could mean increased chance of the cold continental air making it to the British Isles at times, especially if we get a Sudden Stratospheric Warming event, but the lack of a strong signal for easterlies implies that it probably won’t be a particularly cold month overall