Here is a summary of the NWP output for noon on Thursday.
Issued 0529, 9th December 2007

By Thursday there will be a southerly flow over much of the UK as high
pressure builds to the east and NE. It's likely to be the last relatively
mild day for a while over much of the SE half of England, as a Continental
feed becomes established. The further north and west you are, the less cold
it will be and indeed over NW Scotland it's likely to be quite mild for a
time, with strong southerlies keeping temperatures up. It's likely to be dry
for most, although a little drizzle in the SE of England can't be ruled out
if winds have more of an easterly component. The far NW of Scotland is at
risk of rain from Atlantic fronts and night time frosts could be an issue
across much of the UK late next week.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
Low pressure covers Scotland, with strong SW'lies across much of the UK.
Tomorrow the low moves ESE'wards, over the Netherlands, leaving the UK under
NW'lies. A ridge builds over the Irish Sea on Tuesday, introducing a change
in weather type. NW'lies cover much of the UK, although southerlies affect
Northern Ireland. On Wednesday southerlies move over Scotland, Wales and
Northern Ireland, as the ridge builds over England.

T+120 synopsis
http://85.214.49.20/pics/Rtavn12015.png /
http://85.214.49.20/pics/Rtavn1201.png
http://85.214.49.20/pics/Rjma1201.gif /
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 meridonal pattern, with the UK under a large
ridge. At the 500hPa level there's also a large ridge over the UK and it
extends NE'wards to Scandinavia. MetO has an upper high over the North Sea,
with less ridging NE'wards. ECM also has a high over the North Sea, while
GEM brings an upper ridge over the UK. NGP shows an upper high over the
North Sea, as per MetO and ECM.
At the surface GFS brings a ridge over England and Wales, with southerlies
elsewhere. MetO has a high over Germany and southerlies for much of the UK;
the exception is the SE half of England, which lies under easterlies. ECM's
high is centred over southern Sweden, with a ridge over East Anglia. Again,
winds are southerlies for most but this time there are NE'lies for the SE of
England. GEM brings southerlies for all with hhigh pressure over southern
Scandinavia, while NGP has a high over the North Sea and NE'lies for England
and Wales; elsewhere winds are SSE'lies.

Evolution to T+168
ECM shows high pressure over the North Sea on days 6 and 7, with easterlies
for much of England and Wales and southerlies elsewhere.
On day 6 the GFS brings a Scandinavian High, with ENE'lies for England and
Wales and SE'lies elsewhere. Cold air is advected westwards around the
(declining) high on day 7, with brisk easterlies across the UK.

Looking further afield
Day 8 with the ECM shows high pressure declining to the east, with a mixture
of southerlies and SE'lies for the UK. There's little change on day 9 as the
high builds NE'wards, although the southerly winds increase to near gale
force over NW Scotland and Northern Ireland. Day 10 sees strong southerlies
for much of the UK, with lighter ESE'lies over SE and southern England.
The GFS shows ESE'lies on day 8 as the Scandinavian High ridges SE'wards.
The high remains in situ on day 9, with further easterlies and ESE'lies for
the UK. By day 10 low pressure approaches from the west and the high sinks
SE'wards, leading to ESE'lies and SE'lies.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles for London show dry weather on the way, with a probable fall
in temperatures after the 14th.

Special one-off ECM ensemble analysis
(http://www.ecmwf.int/products/d/samp...rope/page.html)
The ECM ensembles for Rochester in Kent are available as today's freebie
from ECMWF. They show a mean high of 6C on the 13th, followed by a slight
fall to a mean of 4 or 5C over the following days as the Continental air
digs in.