It may look benign but I can assure you there is a lot going on and plenty
of "potential".

OK let's start with Christmas. Almost a dead cert for a dry Christmas under
high pressure influence for southern Britain, more windy as you go north.
Pretty mild as well. Northern Britain is far less clear cut as that area is
closest to the developing SW'ly jet. Potential here for very windy and wet
conditions especially the further north you go, though probably mild. The
far north of Scotland and Orkney and Shetland may get into polar air with
increased potential for snow here.

Early next week a very tight low-level baroclinic zone develops in
mid-Atlantic with something like a 15-20 degree airmass contrast due to
persistence of deep cold air in north Atlantic and very warm air flooding
north around the Azores high. Not surprisingly associated with this is a
developing powerful SW-NE jet and global models are struggling developing
numerical instabilities as witnessed on ECM T+120 surface pressure chart
valid for Monday 12Z. (Note closed 1010 hPa low centres). At the left
entrance to this jet there is likely to be a rapid build of pressure which
will be a new high containing much colder air. However, around mid-week the
jet runs away NE leaving behing an interesting disrupting upper trough,.
which has been in evidence on three runs now. That could cause quite a few
headaches, with more extreme solutions like ECM bringing snow across
Scotland before cold air floods south, to probably the more likely outcome
of a spell of heavy rain before the colder air spreads south under the
building high, more like JMA 12Z run. After then probably high pressure with
night frost but where will it sit?

So all in all plenty of interest for the synopticians and potentially some
action too for weather buffs, I'm getting really interested in that
extremely tight baroclinic zone developing on Boxing day onwards as it is
close in distance to global model gridlength scale. Something could
potentially explode into life in there, and it won't be Father Christmas!
:-)

Ciao,

Will
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