?Here is a summary of the NWP output for noon on Thursday.
Issued 0520, 28th November 2010

In summary, the end of the working week will be very cold. Low pressure will
move away to the east, with showers in the east gradually dying out through
Friday as a weak ridge moves in from the NW. As the ridge crosses the UK
some exceptionally cold overnight minima are possible, with -10C looking
quite widespread at present. During the weekend the models show the omega
block moving further west, with its supporting low merging with an Atlantic
low and moving towards the UK. This heralds the risk of heavy - transitory -
snow as the rain encounters the cold air entrenched over the UK. The milder
air is currently forecast to move northwards over the UK, although it's
worth noting that both the GFS and ECM operational runs were on the mild
side compared to their ensembles.

Analysis and evolution to T+120 via GFS
Northerlies and NNE'lies cover the UK, with a low over the North Sea.
Tomorrow the low moves southwards, allowing moderate NE'lies to cover all
areas. NE'lies persist on Tuesday, with a shallow low near Kent bringing a
spell of snow for southeastern areas. A similar low crosses northern
Scotland on Wednesday, with NE'lies elsewhere.

T+120 synopsis
http://www.wetterzentrale.de/wz/pics/Rtavn12014.png
http://www.wetterzentrale.de/wz/pics/Rtavn1201.png
http://www.wetterzentrale.de/wz/pics/Rukm1201.gif
http://www.wetterzentrale.de/wz/pics/Recm1201.gif
http://www.wetterzentrale.de/wz/pics/Rjma1201.gif
The jetstream chart shows a distorted omega block SW of Greenland, with the
UK - and much of western Europe - under a marked trough. At the 500hPa level
there are NE'lies, with an upper low to the east and a ridge to the NW. MetO
also shows upper NE'lies, as a ridge moves southwards to the west of the UK.
The other models also show upper NE'lies, with JMA having a relatively deep
upper low to the east compared with the other models.
At the surface, GFS brings light NNE'lies with a high to the immediate north
of Scotland and a low over northern France. The Met Office model shows a
ridge over Scotland and Northern Ireland, with NNE'lies elsewhere. ECM has a
weaker ridge over northern Scotland and NE'lies across the UK, while GEM has
a similar setup with lighter NNE'lies as a result. JMA has a low over the
Netherlands, with northerlies for the UK.

Evolution to T+168
ECM shows a ridge over Scotland and Northern Ireland on day 6, with NNW'lies
elsewhere. The ridge moves eastwards on day 7, leading to light winds across
the UK.
GFS brings a very cold ridge over the UK on day 6, followed by SE'lies ahead
of a low to the SW on day 7.

Looking further afield
ECM shows a col for Scotland and the NE half of England on day 8, with a
deep low to the SW and ESE'lies for the SW half of England, as well as Wales
and Northern Ireland. Easterlies spread across all areas on day 9 as a
secondary low forms over Biscay. Day 10 sees the secondary low move over the
North Sea, introducing NNE'lies to Scotland and Northern Ireland, with
southerlies for the Midlands south.
Day 8 with GFS brings ESE'lies over most areas, together with much milder
air spreading from the south. A trough covers the Scottish borders on day 9,
with easterlies in advance and mild southerlies to the south. Southerlies
and SSE'lies cover the UK on day 10, with low pressure to the west.

Ensemble analysis
http://www.meteociel.com/cartes_obs/...&ville=Londres
The GEFS shows the very cold spell coming to an end next weekend, although
the 0z run was one of the quickest at bringing back mild air.

ECM ensembles
http://www.meteogroup.co.uk/meteo/ep...tt6-london.gif
The ECM ensembles also show a warming-up next weekend, although again like
the GFS the operational was ahead of the pack in terms of warmth.