A few observations on December circulation types. Jn his book "The English Climate,the author H.H.Lamb.identified singularities of various weather types.For December he identified the 17-24th as December Continental Anticyclones.He describes the typical circulation development as " anticyclonic development over central and sometimes nor,Europe tends to occur through spread (or movement) of the Siberian winter towards N Russia (and Scandinavia ) from 9/12 onwards and development of Highs over France- central Europe in former maritime air about 20/12.
So Anticyclonic weather is no stranger to December.If asked which winter month has the highest level of blocking ie NAO- circulation many of us I suspect would go for February.In fact over the last seventy winters the proportion of winter months having an NAO - circulation are December 49%,January 33% and February 39%.
Hope that puts things in context -but I would still expect December 2015 to be NAO +.
Originally Posted by: roger63