Here is a summary of the NWP output for 12z on Wednesday.
Issued 0550z, 12th February 2007.

The outlook continues to be unsettled for Friday and Saturday, although a
weak ridge might give a brief respite from the rain on Sunday.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
http://85.214.49.20/pics/avnpanel1.gif
A deep low lies to the west, leading to southerlies and SW'lies for the UK.
Tomorrow the low moves over the North Sea, leaving westerlies for all. By
Wednesday a new low lies to the SSW, resulting in southerlies for most
areas. The low moves over the Netherlands on Thursday, with a weak ridge
over England and Wales. Elsewhere winds are southerlies due to a deep low to
the west.

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 the UK under a shortwave trough, with an intensely
strong jet heading eastwards towards the Azores. At the 500hPa level there's
a ridge to the east, a trough over the UK and a deep upper low over Iceland.
MetO is broadly similar, although the ridge to the east is stronger and the
low near Iceland is further north and less deep. ECM has less of a ridge to
the east and the UK trough is further west. NGP is very similar to GFS,
while GEM has a deeper trough affecting Ireland in particular.
At the surface GFS brings light southerlies and SSE'lies over the UK, due to
a weak trough over Ireland. MetO has a trough over the Irish Sea with
stronger SSE'lies in advance and NW'lies following behind. ECM brings a
trough over Ireland with SSW'lies for all, while NGP is a bit more
progressive with the trough over Wales. To the east winds are SSE'lies, to
the west they're southerlies. The Canadian run brings complex low pressure
close to the west, with southerlies and SSE'lies for the UK.

Evolution to T+168
ECM shows the trough over the UK disrupting. Day 6 sees westerlies for the
UK as a ridge moves over England and Wales. By day 7 SW'lies and southerlies
affect the UK as pressure builds to the east.
GFS also shows trough disruption, with a low moving SE'wards over Italy. Day
6 sees a ridge over the UK, leading to WNW'lies for England and Wales,
SW'lies for Northern Ireland and WSW'lies for Scotland. By day 7 a low
approaches from the west, with SSE'lies and SE'lies for the UK.

Looking further afield
ECM shows complex low pressure to the north and NW on days 8 and 9, with
SW'lies for the UK. On day 10 a secondary low approaches from the SW,
bringing southerlies to the UK.
GFS also shows SW'lies for the UK with a deep low to the NW on days 8 to 10.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles show a dramatic "sine wave" effect for London with 10mm of
rain on Wednesday. Further north the temperature plot is flatter but there's
still a fair bit of rain. Both sets of ensembles have a couple of much
colder runs, but the majority retain average or above average temperatures
throughout.