Here is a summary of the NWP output for noon on Monday.
Issued 0523, 13th December 2007

The middle of the week is likely to see our blocking high sinking slowly
SE'wards, bringing SE'lies or ESE'lies for much of the time. Towards next
weekend both the ECM and GFS restore a zonal SW'ly flow for the UK.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
High pressure lies to the NE, with southerlies across much of the UK.
There's little change tomorrow as the high sinks southwards and by Saturday
the high declines slightly. By then southerlies persist across Northern
Ireland and Scotland, with a ridge bringing light winds elsewhere. On Sunday
the high builds over the southern Baltic, with easterlies for England and
Wales and southerlies continuing elsewhere.

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 the jet splitting to the west, with a diffluent
block over the UK. Most of the energy is going to the northern "arm" of the
jet and the UK lies under a large ridge. At the 500hPa level there's an
upper high over the North Sea and upper lows to the SW and SE of the UK.
MetO features an upper high over Scandinavia and an upper low over the
English Channel. ECM has an upper high over southern Scandinavia and a low
over southern France, while NGP has an upper low over Biscay and a high over
southern Scandinavia. GEM centres an upper high over the North Sea, with
just a trough over southern Europe instead of a cut-off low.
At the surface GFS brings a high to the NE and a mixture of SE'lies and
easterlies for the UK. MetO has ESE'lies for all and potentially some
wintriness over southern parts of the UK due to the upper low caught up in
the flow. ECM brings a high over the North Sea and ENE'lies over England and
Wales; elsewhere winds are SE'lies. NGP's high is further south, over
Germany, leading to a mix of easterlies and southerlies for the UK. GEM has
SE'lies for most with a high over the Netherlands.

Evolution to T+168
ECM shows moderate ESE'lies over the UK on day 6 as the high moves ESE'wards
and a trough approaches from the south. The trough moves westwards as a new
high centre forms to the north of Scotland on day 7. Moderate easterlies and
ESE'lies cover the UK as a result.
On day 6 the GFS shows easterlies across England and Wales, with SE'lies
elsewhere dut to a high over Poland. The high moves south on day 7, leaving
the UK under a mixture of ESE'lies and southerlies.

Looking further afield
Day 8 with the ECM shows ESE'lies and SE'lies for the UK, with high
pressure to the NE and a low to the west. The low moves northwards on day 9
and the high moves SE'wards, allowing SE'lies and SSE'lies to affect the UK.
By day 10 SW'lies cover the UK as pressure builds to the SW.
The GFS shows strengthening SE'lies for most on day 8 as a low approaches
from the SW. By day 9 the low moves NE'eards and deepens, with strong
southerlies over the UK. By day 10 SW'lies cover all areas, with low
pressure to the NNW.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles for London continue to show the dry spell ending in a week's
time, just as with yesterday's output.

Just for fun!
*A daily look at charts for 12z on Christmas Day*, not to be taken seriously
at this range of course.
GFS - http://85.214.49.20/wz/pics/Rtavn3001.png
Low pressure is centred over the North Sea, with the UK under a mixture of
westerlies and WSW'lies. Snow potential: low, except for high ground over
Scotland.