Here is a summary of the NWP output for noon on Monday.
Issued 0538, 11th December 2008

The models show a battle looming next week. A strong, zonal jet upstream
will lead to low pressure near to the UK, but a large high will build to the
NE and this will impede the progress of Atlantic systems. ECM deals with
this by forcing a trough to disrupt on Tuesday, leaving the UK in
no-mans-land on Wednesday and bringing SW'lies by Thursday.

GFS doesn't disrupt Tuesday's trough, but it still brings a col midweek.
Again, by Thursday a SW'ly flow affects the UK. Thus, at present it's likely
there'll be a nondescript spell midweek, followed by a return to milder,
more mobile conditions by the end of the working week. Given recent model
performance, though, confidence isn't especially high today!

Analysis and evolution to T+120 via GFS
A shallow low covers the North Sea, with a col and light winds over the UK.
Tomorrow the low fills, still with a coll for most. Saturday sees strong to
gale force southerlies spreading eastwards in association with a trough. The
trough disrupts on Sunday, leading to light easterlies for most.

T+120 synopsis
http://85.214.49.20/pics/Rtavn12014.png /
http://85.214.49.20/pics/Rtavn1201.png
http://85.214.49.20/pics/Rukm1201.gif
http://85.214.49.20/pics/Recm1201.gif /
http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a zonal flow over much of the Atlantic, with a
ridge over the UK. At the 500hPa level there's also a ridge over the UK, as
is the case with MetO. ECM has a disrupting trough over the UK instead,
while GEM brings an upper ridge as per GFS and MetO.
At the surface, GFS shows a col for England and Wales and SW'lies elsewhere.
MetO has a col over much of the UK, with NE'lies for the SE half of England.
ECM brings a trough over the Irish Sea, with SSE'lies in advance and
westerlies following behind. A col covers much of the UK with GEM.

Evolution to T+168
Day 6 with ECM shows complex low pressure over the North Sea, with a mixture
of WNW'lies and WSW'lies over the UK. On day 7 the winds become WNW'lies as
low pressure fills over the North Sea.
On day 6 with GFS a col covers the UK. Day 7 sees a trough move eastwards,
with WSW'lies for all.

Looking further afield
Day 8 with ECM shows SW'lies for many as a trough approaches from the west.
SW'lies persist on day 9 and on day 10 the winds become westerlies due to a
secondary low over the North Sea.
A strong SW'ly flow covers the UK on days 8 to 10 with GFS, with complex low
pressure over Ieland and a high building over central Europe.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles continue to show a zonal outlook. Notably, today's operational
run was a markedly mild run from as early as T+60.

Christmas Countdown
**NOTE: The following section is provided on a "for fun" basis and is not to
be used operationally. Remember, temperatures can go down as well as up and
nothing is gauranteed when it comes to weather! **

http://91.121.93.17/pics/Rtavn3361.png
The operational GFS shows a WSW'ly flow over the UK, with the Azores High
displaced towards the UK and a deep low east of Iceland. Temperatures are
around average.

Ensemble wise, the members are split as follows:
SW'lies: 8
Southerlies: 2
NW'lies: 2
Col: 1
Easterlies: 2
Westerlies: 5
High pressure or ridge over UK: 1 (inc control)

The most likely outcome today remains a SW'ly flow over Christmas, but a
southerly flow is now less likely compared to yesterday. Instead, the second
most likely outcome is a relatively cool westerly flow. Either way, it's
still looking like only the hills in the north will see a White Christmas.