There are some changes which may be of interest - a stratospheric warming
event likely to start in the next few days running into N America and then
maintained to the end of GFS run with support from EC. The polar vortex is
relocated from NE Canada /NW Greenland 80W to off the N of Russia 80E but is
not forecast to split as in the Jan 2009 winter, which in that case led to a
reversal of the westerly over UK/Europe.

Interesting to see what impacts result from a late December more northerly
stratospheric flow over UK - of course forecasts can change!.

Not sure if this stratospheric change is the reason that CFS2 monthly
forecast for Jan 2013 jumped from cold over UK to above normal temps in runs
after 2 DEC. Similar changes to less cold can be seen in other seasonal
output including MO which now has a less cold JFM than earlier runs. Some
seasonal output has indicated very high positive temperature anomalies
across N Scandinavia and N Russia for Jan (eg NASA GSM output). SO far MO
seasonal has been correct at indicating colder than normal.

Most web available seasonal output over the last several months has been
poor with regards to precipitation but those that signal less cold temps
this time also show above normal precipitation.

Seasonal output from IRI, JMA and KMA still to come so may be able to see if
later data suggest anything different.