Eskimo Will wrote:
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
--


------------------------
Yes, I think next January will be far more interesting than this year.
We were very unlikely to get a repeat of last December but I've found
this December very interesting and variable. Much better than last Jan
and Feb for sure.
Dave