Here is a summary of the NWP output for noon on Wednesday.
Issued 0522, 12th December 2009.

The end of the working week will see calmer, quieter conditions moving
southwards across the UK as the cold NE'ly feed moves away to the south.
Despite the higher temperatures aloft, widespread and locally severe frosts
are possible as skies clear and winds fall light.

Analysis and evolution to T+120 via GFS
High pressure lies to the NE, with NE'lies setting in across much of England
and southerlies or SE'lies elsewhere. Tomorrow the high declines over
Scotland, with NE'lies for England and Wales and SE'lies for Northern
Ireland. Monday sees the high cover Scotland and Northern Ireland, with
further NE'lies elsewhere. On Tuesday a low moves southwards over the North
Sea, with a col over England and northerlies elsewhere.

T+120 synopsis
http://91.121.93.17/pics/Rtavn12015.png /
http://91.121.93.17/pics/Rtavn1201.png
http://91.121.93.17/pics/Rukm1201.gif
http://91.121.93.17/pics/Recm1201.gif /
http://www.meteociel.fr/modeles/nogapse_cartes.php
The jetstream chart shows a diffluent block over the Atlantic, with a ridge
over Iceland and a trough over the UK. At the 500hPa level it's similar,
with a high over Iceland and a trough extending westwards over England and
Wales. ECM has a similar setup, with a high over Iceland and a trough
working its way SW'wards over the UK. MetO has an upper high further south,
to the WNW of the UK and as such there's an upper NNE'ly feed rather than an
upper ENE'ly flow for the UK. GEM is unavailable and JMA brings upper
northerlies with a high to the NW and a trough to the SE.
At the surface, GFS brings NE'lies for all with highs to the NW, NE and a
low to the SW. ECM has a small low over the southern North Sea, with
NNE'lies and NE'lies as a result. MetO also has NW'lies with a low over
Northern France. JMA meanwhile brings northerlies with a high to the WNW and
a low over the Netherlands.

Evolution to T+168
ECM shows strong to gale force ENE'lies on day 6 as high pressure moves
SW'wards to the north and low pressure moves southwards over France. The
winds ease across England and Wales on day 7 as a ridge sinks southwards;
this brings much milder NW'lies over Scotland.
A ridge covers Scotland on day 6 with GFS, with strong ENE'lies elsewhere.
Day 7 sees a col over the UK, with westerlies in the far north and ENE'lies
persisting in the far south.

Looking further afield
ECM shows NW'lies on day 8 with complex low pressure to the NE. The lows
sink SW'wards on day 9, with strong westerlies for the UK. By day 10 low
pressure covers the UK.
Days 8 to 10 with GFS show low pressure moving eastwards from the Azores to
Biscay. Northerlies ease on day 8, with just light NW'lies on day 9. Day 10
sees a cold col over the UK.

Christmas Day chart watch
http://www.wzkarten.de/pics/Rtavn3121.png
The chart for Christmas Day shows northerlies and NE'lies over the UK with
lows to the east and SW. Conditions are conducive for sleet or snow across
most of the UK, with the exception of the far SW.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles show a "sine wave" reverse zonal pattern for the next 10 days
or so.

Christmas countdown:
For midnight on Christmas Day, the ensembles show the following:
Southerlies / SE'lies: 6
Easterlies/NE'lies: 6
Low over UK: 3
Westerlies / SW'lies: 6

The ensembles are mixed today, with no overall winner. It looks as though an
upper trough will be close to the UK, the remnants of our current block.
However, there's disagreement over the westwards extent of the trough, with
many runs having us on the "warm" side as it's retrogressed so much!