Here is a summary of the NWP output for 12z on Sunday.
Issued 0543z, 8/11/06

The models show signs of a change today. The GFS and ECM both point to a
cooler period for next week, although at this range the variance is great.
Nonetheless it looks like the upper ridge that's affected the UK recently
will, in effect, retrogress - but the specifics are still very uncertain at
the moment. As ever, more runs are needed.

Analysis and evolution to T+120 via GFS
http://85.214.49.20/pics/Rtavn001.png
http://85.214.49.20/pics/avnpanel1.gif
The UK lies under WSW'lies and SW'lies, with a shallow trough to the west.
By tomorrow the trough will be moving away to the east, with WNW'lies across
the UK. High pressure will then move eastwards so that by Friday a ridge
covers England and Wales, with SSW'lies elsewhere. Another trough approaches
from the west on Saturday, with SW'lies across England and Wales; elsewhere
winds are westerlies.

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 jet stream chart shows a ridge to the west of the UK, with a powerful
jet heading eastwards towards Iceland and SE'weards over Scandinavia and
Germany. At the 500hPa level a high lies to the SW with a NW'ly gradient
over the UK. A marked trough covers Scandinavia. MetO shows an upper ridge
over the UK with a much deeper low over Iceland, while ECM also shows a
ridge over the UK. JMA and NGP both show an upper ridge to the west of the
UK.

At the surface, GFS shows a weak ridge over the UK with a high to the south.
Winds are moderate westerlies for all, whereas with MetO the winds are
stronger SW'lies with a ridge to the east. ECM shows SW'lies, again with a
ridge to the east. NGP brings westerlies for all and JMA has a high to the
WSW with NW'lies as a result.

Evolution to T+168
ECM shows the Icelandic low deepening and moving eastwards at T+144,
bringing a trough and strong westerlies across the UK. The winds become
WSW'lies at T+168 as the low becomes slow moving to the north.
Complex low pressure lies to the north on day 6 with the GFS, leading to
westerlies across the UK. The winds become WSW'lies at T+168 as the lows
move eastwards.

Looking further afield
ECM out to 10 days shows low pressure moving eastwards over Scandinavia with
pressure building over the mid-Atlandic. Northerlies and NW'lies cover the
UK, followed by more of the same on day 9. By day 10 the Atlantic ridge
sinks SE'wards over Ireland, leaving the UK under NW'lies.
The GFS brings a trough over the UK on day 8 with light westerlies and
NW'lies. This heralds a marked change, with high pressure extending
southwards from Greenland. By day 9 the high is still there, with moderate
NNW'lies over the UK. Day 10 sees the high recentre over the mid-Atlantic,
with further northerlies for the UK.

Ensemble analysis (http://85.214.49.20/wz/pics/MT8_London_ens.png - last
night's 18z)
The ensembles show marked divergence as early as T+96, but it's now looking
likely there'll be a shot of cold air across the UK on Sunday. Beyond that
the ensembles show temperatures recovering for the start of the week, before
falling again as a northerly sets in. However, there are great differences
regarding the intensity and duration.