Here is a summary of the NWP output for 12z on Thursday.
Issued 0523z, 21st January 2007.

The models show hints of a change today. MetO doesn't collapse the high at
T+144, instead it retrogresses slightly and opens the gates to an extra push
of cold air from the north. GFS develops a Baltic High deep in the realms of
fantasy, but the seeds are sown as early as T+144 when an upper high appears
to the far NE; it's not supported by the other models at this stage though.
In the meantime we've a cold week ahead but with temperatures probably
returning to normal by the weekend.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
http://85.214.49.20/pics/avnpanel1.gif
Strong and gusty westerlies cover much of the UK in association with an
eastwards moving low over Scandinavia. A trough sinks SE'wards over the UK
tomorrow as pressure builids to the SW of Iceland. Ahead of the trough winds
are WSW'lies, with northerlies following behind. Northerlies and NNW'lies
affect the UK on Tuesday as the high builds to the west of the UK. The high
moves SW'wards on Wednesday, allowing NW'lies to affect all areas. By
midnight on Thursday it moves slight northwestwards as a ridge topples over
the UK. Winds are northerlies for most, with NW'lies for NW Scotland.

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://85.214.49.20/pics/Rngp1201.gif
The jetstream chart shows a large ridge over the North Atlantic, with a weak
jet heading northwards to Greenland and a weaker jet still heading
southwards over the UK. At the 500hPa level there's a high to the SW and the
equivalent of a warm sector over the UK. MetO shows something similar, with
a high to the WSW. ECM shows an upper high to the west, as is the case with
JMA. NGP and GEM have the uper high to the WSW instead.
At the surface GFS shows an elongated Azores High to the west and NW'lies
across the UK. MetO also shows NW'lies, with a stronger Azores High. ECM has
a ridge from the west over England and Wales, bringing NE'lies to the far
south and NW'lies elsewhere. JMA has the ridge further south with WNW'lies
and NW'lies as a result, while NGP has NE'lies across England and Wales from
a ridge (with westerlies elsewhere). Finally GEM brings NW'lies across the
UK, again with the Azores High to the west.

Evolution to T+168
ECM shows the Azores High building and moving slowly SE'wards. Day 6 sees
NW'lies for all as the high passes Ireland, followed by WSW'lies and
westerlies on day 7 as it builds over Biscay.
GFS also collapses the upper ridge SE'wards, albeit with colder air over the
UK due to an aborted northerly. WNW'lies cover the UK on day 6 with the
Azores High to the SW, followed by westerlies and WNW'lies on day 7 as it
moves over Iberia.

Looking further afield
Beyond T+168, ECM shows WSW'lies out to day 10 as high pressure persists
over France.
GFS shows the remnants of the upper mid-Atlantic ridge moving over the UK on
day 8, with westerlies and SW'lies. Far to the north of Svalbard there's a
small upper high and it persists on day 9. Meanwhile heights rise to the
south of Iceland as a low moves swiftly eastwards to the north of the UK.
Winds are strong westerlies for all. On day 10 the height rises near Iceland
continue in the form of an upper ridge to the west of the UK. The ridge
links to that upper high near Svalbard, drawing very cold air southwards
over Scandinavia. For the UK things are more benign, with a ridge over
Ireland and a mixture of NNW'lies and NW'lies as a result.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles show a cold working week ahead, with milder air returning from
the NW as the weekend approaches.