Here is a summary of the NWP output for 12z on Sunday.
Issued 0528z, 18th April 2007.

The working week will start with a split over the UK. Northern and western
areas are likely to see cloud and possibly rain, while southern and eastern
areas should be brighter and drier. By the middle of the week most areas
will have seen rain as an active trough moves in from the Atlantic.
Temperatures will generally be above average.

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 large high is centred near Ireland, leading to light winds across all
areas except parts of Scotland. Tomorrow a trough passes close to Scotland,
bringing stronger WSW'lies there; elsewhere winds remain light. On Friday
high pressure covers Scotland, leading to easterlies elsewhere. By Saturday
the high moves away to the east, introducing southerlies and SSW'lies for
the UK.

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 UK under a ridge, with a weak SW'ly gradient
at the 500hPa level. ECM shows a similar picture, with a weak ridge to the
east, while MetO keeps the ridge further west, over the UK. GEM shows a
series of upper shortwave troughs in the vicinity of the UK, while NGP is
unavailable today.
At the surface GFS brings light SW'lies and SSW'lies, with a high far to the
SE and a low over the mid-Atlantic. ECM shows SSW'lies and southerlies as
well, this time with a high over Poland. MetO has a weak ridge with a
mixture of westerlies and SW'lies for the UK, while GEM shows a weak trough
over Ireland and SW'lies for all.

Evolution to T+168
Southerlies cover the UK on day 6 of the ECM, before an active trough sweeps
NE'wards on day 7, bringing southerlies in advance and westerlies behind.
GFS brings a trough over the UK on day 6 with southerlies in advance. By day
7 the UK lies under westerlies, with the trough by now to the north of
Scotland.

Looking further afield
ECM shows a col for the UK on days 8 and 10, with a trough over England and
Wales and light easterlies for most on day 9.
GFS brings a shallow low and light winds over the UK on day 8, followed by
SW'lies on day 9 as pressure builds over Biscay. By day 10 a ridge covers
England and Wales with westerlies; elsewhere winds are SW'lies.

Ensemble analysis
(http://expert.weatheronline.co.uk/da...ia/ensdia.html - last
night's 18z)
The ensembles now show above average temperatures for northern areas from
day 3 until day 7, followed by slightly above average temperatures. Further
south temperatures are generally above average on the whole 16 day run.

In uk.sci.weather on Wed, 18 Apr 2007, Darren Prescott
wrote :

Here is a summary of the NWP output for 12z on Sunday.
Issued 0528z, 18th April 2007.

The working week will start with a split over the UK. Northern and western
areas are likely to see cloud and possibly rain, while southern and eastern
areas should be brighter and drier. By the middle of the week most areas
will have seen rain as an active trough moves in from the Atlantic.
Temperatures will generally be above average.

The 1971-2000 averages seem ever less relevant, though...
--
Paul Hyett, Cheltenham (change 'invalid83261' to 'blueyonder' to email me)