Here is a summary of the latest NWP output for noon on Thursday. Issued
0714z, 14/12/03.

ECMWF: http://www.wetterzentrale.de/pics/Recm1201.gif
A ridge covers England and Wales, bringing southerlies or SE'lies to
southern and central areas of England and Wales. To the north, winds are
westerlies, due to a deep low to the east of Iceland. A weak high lies to
the south of Greenland and it builds as it moves eastwards at T+144. This,
combined with the low moving NE'wards, allows NW'lies over the UK. By T+168
the high is absorbed by a Greenland High, forcing another low SE'watds
towards the UK. Westerlies and NW'lies cover the UK in advance of the low.

MetO: http://www.wetterzentrale.de/pics/Rukm1201.html
The Met Office run shows a ridge over much of the UK, bringing light winds
for most. The exception is northern Scotland, which lies under moderate
WNW'lies. The ridge builds over the UK at T+144, with southerlies, SW'lies
and westerlies as a result.

GFS: http://www.wetterzentrale.de/pics/Rtavn1081.gif
Low pressure lies to the north, with a ridge extending southwards from
Greenland, then SE'wards to the south of Ireland to France. WNW'lies are the
result across the UK; by T+120 the winds become NW'lies as pressure rises to
the west and SW of Iceland. 850hPa temperatures range from -4C over Northern
Ireland and southern Scotland to +3C over SW England. Light northerlies
cover much of the UK at T+144, as the high builds and sinks SE'wards over
Ireland. The high moves SE'wards over southern Germany by T+168, leaving
WSW'lies over the UK. SW'lies cover the UK on days 8 and 9, as a low tracks
ENE'wards to the south of Iceland. By day 10 another low lies to the west of
Scotland, with southerlies for Scotland and SW'lies elsewhere.

GEM: http://www.wetterzentrale.de/pics/Rgem1201.gif
The Canadian run shows a ridge to the south and SW of the UK, while low
pressure lies to the north. This leads to WNW'lies and westerlies, with
850hPa temperatures ranging from -1C over Scotland and Northern Ireland to
+5C over SW England. A weak ridge moves over the UK at T+144, with
westerlies for all.

JMA: http://www.wetterzentrale.de/pics/Rjma1201.html
A ridge from the SE covers the UK, leading to SSE'lies for much of England
and Wales, while Scotland and Northern Ireland lie under westerlies and
SW'lies respectively. 850hPa temperatures vary from +3C over northern
Scotland to +7C over southern Scotland and northern England. A high leaving
Newfoundland merges with the Greenland High at T+144, forcing the main
Atlantic low eastwards to the WNW of the Azores. Two shallow lows lie to the
NE of the main low, leading to SW'lies over the UK. The SW'lies become
stronger at T+168 as the two small lows merge and move NE to the north of
Scotland. The high to the south of Greenland builds further so that by day 8
it blocks the Azores low from moving NE'wards. Instead, the low to the north
of Scotland deepens and moves eastwards over southern Norway, with strong
northerlies and westerlies for the UK as a trough sinks southwards.

Christmas Day charts:
http://129.13.102.67/wz/pics/Rtavn2641.gif
http://129.13.102.67/wz/pics/Rtavn2642.gif
http://129.13.102.67/wz/pics/Rtavn2643.gif
http://129.13.102.67/wz/pics/Rtavn2644.gif

(Reminder: This is still in the realm of fantasy charts, so don't take this
too seriously. Also, I'll handle this section differently from tomorrow
onwards, as Christmas Day will be making its debut appearance on a variety
of other runs.)

The chart for Christmas Day shows a deep low to the south of Iceland, with a
weak ridge over the North Sea. Winds are WSW'lies or SW'lies over the
majority of the UK, although northern Scotland lies under southerlies.
850hPa temperatures vary from -1C over northern Scotland to +1C over
southern England, while thicknesses range from 532dam over northern Scotland
to 541dam over southern England. Precipitation is shown as having affected
much of the UK except northern England. Snow is likely across Scottish
mountains as a result, but there's not much chance at more habitable levels.


In summary, the runs today are mixed, even at a range of 108 or 120 hours.
The basic picture is of a ridge initially bringing settled conditions for
southern areas of the UK, with less settled weather for northern areas.

However, beyond that things could evolve in two different ways: either high
pressure leaving Canada merges with the Greenland High, forming a block with
cooler conditions (northerlies, NW'lies or westerlies, as shown by JMA and
ECM). Alternatively, the high could instead sink SE'wards over Europe,
bringing settled conditions at first followed by mild westerlies or SW'lies
(GFS, GEM). As the outcome will determine whether we get a cold or mild few
days before Christmas, as ever more runs are needed.