Interesting stuff going on with the models at the moment. The pattern that GEM has been showing for a few days now in the 8-10 day range is not one I'm all that familiar with, which means I'm not really sure what sort of model behaviour to anticipate.
At the moment, GEM is gaining ever more support from ECM, while GFS is slowly edging in that direction. The main reason for this is that the latter two are seeing stronger ridging into the Arctic with each new run, causing the PV more trouble. ECM develops that into a major displacement unfolding by day 10 - in the theme of GEM. GFS shows the Atlantic more love, choosing to split the PV between Siberia and the U.S. - which means the Atlantic storms can still get a good kick as they cross towards the UK.
The fact that GFS fails to regroup the PV by day 16 is a good sign IMO.
Overall, there is more of a signal for a cold spell not far into December. The magnitude remains highly uncertain, and my personal hope is that it serves only as a taster of things to come late in the month
Originally Posted by: Stormchaser