http://modeles.meteociel.fr/modeles/cfs/run/cfsnh-0-1140.png?18
This is a classic CFS-type cold spell chart; there is higher pressure in the Arctic and some high-lat blocking, but at the same time the PV energy remains vigorous and continues to fight against the high pressure.
Before too long, the inevitable crazy chart materialises, albiet not for the UK directly:
http://modeles.meteociel.fr/modeles/cfs/run/cfsnh-0-1350.png?18
One of the most extreme Siberian storms in recorded history!
The frequency of December cold spells in the CFS runs seems to have been on the rise over the past fortnight. I'm not the best judge of that though; not had much time to view the individual runs lately.
The above CFS run produces a largely westerly winter from late December onwards, often very stormy. The PV is heavily displaced at times, but remains too powerful, driving vicious storms at the UK and overcoming the high-latitude blocking that tries to develop to our NE. Factor in the CFS tendency to overdo the PV energy and things could turn out very differently!
Originally Posted by: Stormchaser