Here is a summary of the NWP output for 12z on Wednesday.
Issued 0611z, 25/11/06

The outlook remains unsettled for all in the short term, with low pressure
close by and temperatures largely above average. There are hints (and only
tentative ones at this stage) of cooler weather spilling over the UK in the
8 to 10 day period due to mid-Atlantic ridging, but confidence is very low.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
http://85.214.49.20/pics/avnpanel1.gif
Low pressure lies to the west with a secondary low to the SW. Strong winds
and very mild air cover SE England, with lighter SW'lies or southerlies
elsewhere. The low moves away to the north tomorrow, with SSW'lies and
SW'lies across the UK. Monday sees a deep low to the west with southerlies
for all, followed by further southerlies on Tuesday as the low fills and
moves slowly northwards.

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.jpg /
http://85.214.49.20/pics/Rukm1201.jpg
http://85.214.49.20/pics/Recm1201.jpg /
http://85.214.49.20/pics/Rngp1201.jpg
The jetstream chart shows a shortwave pattern across the North Atlantic,
with a shallow trough to the east, a ridge to the west and a NW'ly flow over
the UK. At the 500hPa level the UK lies under a ridge, with a trough to the
west. MetO has a similar setup, albeit with a stronger ridge to the east.
ECM shows a flatter flow with less of a trough to the west and more of a
WSW'ly rather than SW'ly gradient over the UK. JMA shows a similarly flat
picture for the UK, although the ridge to the east is closer and stronger
than with ECM. NGP and GEM also show a shallower trough to the west and a
WSW'ly gradient over the UK.
At the surface GFS has a high over France and a mixture of WSW'lies and
SW'lies for the UK. MetO brings southerlies across the UK as the result of a
high over Germany and a low to the west. ECM and JMA instead show SW'lies
with high pressure over Iberia and Biscay. GEM and NGP are similar, with low
pressure to the NW (rather than the west as with GFS and MetO); they also
show SW'lies for the UK.

Evolution to T+168
ECM shows the upper trough to the west filling and a new upper ridge
building to the east, with its centre over Germany and the Czech Republic.
At the surface a large high is centred over Germany at T+144, with SSW'lies
and southerlies for the UK. The southerlies and SSW'lies persist at T+168 as
a trough approaches from the west. Meanwhile the high builds and moves
eastwards over the Czech Republic.
The GFS shows a more progressive outlook, with the upper trough to the west
moving eastwards over the UK by day 7. A surface trough approaches from the
west on day 6, leading to strong southerlies for all. On day 7 another
trough approaches from the west with SW'lies and WSW'lies as a result.

Looking further afield
ECM shows an increasingly zonal flow aloft, with westerlies over the UK on
days 8 to 10 as lows move eastwards well to the north of the UK.
GFS also shows a zonal flow for day 8, with a deep upper low near Iceland
and a marked upper high over the Azores. Winds over the UK are westerlies,
strong to gale force (even severe gale force in the north). The upper low
deepens and moves over southern Scandinavia on day 9, with heights falling
below 500dam. Meanwhile an upper ridge develops to the south of Greenland,
leading to a surface ridge in the same area from the Azores High. Strong to
gale force WNW'lies are the result for the UK, followed by strong NW'lies on
day 10 as both the ridge and low move eastwards.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles yet again show a "sine wave" effect for the next week as lows
pass the UK. Beyond that there's a marked cooling trend, with the London
850hPa average hovering around -5C by the end. There's unusually good
agreement for a 16-day range.

*One off ECM ensemble analysis*
Today's ECM freebie is the ensemble plot for Reading:
http://www.ecmwf.int/samples/d/banner/page.html
A similar "sine wave" effect to the GFS charts is visible to start with,
before a great deal of scatter develops around Thursday. Beyond that the
mean temperatures fall away, but it's notable that the progressive
operational run was a marked mild outlier.