Here is a summary of the NWP output for noon on Saturday.
Issued 0531, 27th October 2009

The models show the end to our warm spell. A trough will move swiftly across
the UK on Sunday, bringing rain for all, followed by blustery westerlies and
more rain as pressure falls. It'll turn much colder than of late, albeit
only to average or just below.

Analysis and evolution to T+120 via GFS
Southerlies and SSE'lies cover the UK, the result of a high to the east and
a trough to the west. Southerlies will persist for the rest of the week and
into the weekend, drawing unseasonably warm air over the UK.

T+120 synopsis
http://91.121.93.17/pics/Rtavn12014.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 strong jet heading ENE'wards over the eastern
Atlantic and the UK. At the 500hPa level GFS shows a strong SW'ly flow,
something which is duplicated in all the other runs (ECM, MetO, GEM and
JMA).
At the surface, the models all show SSW'lies over the UK, ahead of a trough,
with the GFS showing a secondary low forminmg in the trough.


Evolution to T+168
Days 6 and 7 with GFS show blustery westerlies, as a strong zonal flow
affects the UK. ECM has a trough crossing the UK on day 6, with southerlies
in advance and westerlies following behind. On day 7 the trough moves away
to the east, allowing lighter NW'lies to affect the UK.

Looking further afield
ECM shows a low west of Ireland on day 8, with southerlies for the UK. The
low fills to the ESE on day 6, with a col over Scotland and NW'lies or
WNW'lies elsewhere. There's little change on day 10.
Day 8 with GFS shows strong westerlies due to a deep low to the NE. A
secondary low approaches from the west on day 9, with westerlies for all. On
day 10 the low deepens over the Netherlands, dragging cold NW'lies over the
UK.

Ensemble analysis
(http://91.121.94.83/modeles/gens/gra...ille=Lond res)
The ensembles continue to show a warm week ahead, with a marked change to
colder conditions at the turn of the month.