We're probably looking at an Atlantic ridge/perhaps UK high initially, largely I suspect driven by the recent +AAM tendency, we then see the MJO move into more favourable phases during the first part of December which should reinforce the +AAM by the way of further +FT and +MT, adding westerly momentum into the atmosphere which will hopefully inject some oomph into the system for amplification/retrogression.
Unsure if we're looking at a Greenland or Scandinavian high, perhaps a mixture of both,. albeit I'd probably favour an extension into Scandi initially, this is mostly dependent on where the vortex lobes end up.
We do have a good shot at something colder/blocked into the 2nd half of December though, background drivers are pointing towards that and have been for a little while. In terms of the MJO;