The AVERAGE PRESSURE CHART FOR THE PERIOD 11th to 23rd December shows
cyclonic WSW to WNW conditions in the northern half of the country and
anticyclonic WNW conditions in the southern and SW part of the country.
So we can expect a large number of days with LP to our N and NW and a
few fleeting glimpses of HP coming out of the SW and rushing off to
the E. Temperatures will be generally slightly above average for most
of the period, however, the occasions when HP covers the country could
bring the daytime temperatures down through frost and fog. Generally
the N and NW of the country should have the most rain throughout the
period, while the S and SE should be relatively dryer.

And now in a bit more detail.

On 11th December, a belt of LP from just to the NW of Scotland to N
Scandinavia is moving NE, while HP over the near continent brings SW
winds over Britain. To the SW of us, HP begins to build up during
mid-morning and moves E across southern areas. It's a showery day for
the N and NW but the S has dryer weather with light winds.

On 12th December, a medium sized LP lies to the NW of the British Isles
while an Azores ridge stretches into the SW and S of the country as far
as the North Sea up as far as E Scotland and into Germany. Out in the
Atlantic, a secondary is moving towards the British Isles. Winds over
Britain are light at first, but SW winds in the W and NW of the country
spread E. Some fog and frost over eastern areas, but warmer with some
rain showers in the W spread further E.

On 13th December, a depression near Iceland sends a trough down to E
Scotland Over the British Isles, winds are mostly W. and a secondary
depression in the W'erly airflow is approaching Ireland. HP along the
S and SW coasts is building up by mid-day and is moving E, to join up
with HP near Scandinavia. Weather is still unsettled in most places but
the S should have dryer conditions, especially in the afternoon.

On 14th December, once again a depression is to be found to the NW of
Scotland while a belt of HP from S England to S Baltic moves into
central Europe. A possible wave to the SW of Ireland moves E towards S
England. Winds will be generally SW but light winds in the SE of the
country at first. The N and NW has the showery weather once again and
the SE has the dryer weather.

On 15th December, the parent LP is still on station to the NW of
Scotland while waves cross southern counties into the S North Sea. A HP
ridge into Biscay builds up and moves into the near continent. A
showery day for most places but in the S of the country some heavy
rainfall could occur.

On 16th December, pressure is low to the W and SW of the British
Isles. Some waves could drift NE'wards near Ireland in the warm and
moist SW winds. The weather will be showery in most places.

On 17th December, the low pressure area has moved NE'wards to be N and
NW of Scotland. A secondary LP lies near the Channel bringing much
rain to southern areas. Winds will be generally SW to S over the
country bringing showers to most places.

On 18th December, the LP near Iceland has a trough to Scotland. In the
S, a belt of HP from the Azores-HP has a flat ridge coming into the S
of Ireland, which is slowly spreading E. Although the ridge remains
pretty flat, fairer weather will cover much of the country, but showers
will be seen in the N and NE of the country.

On 19th December, at last, some HP and improving weather. To the W
and NW of Ireland, pressure begins to rise and this joins up S of
Ireland with the Azores ridge. The S half of Britain enjoys HP while
Scotland sees the last of the LP moving away up the Norwegian coast.
Winds will be light and we can expect frost and fog becoming widespread,
early and late.

On 20th December, an HP centre sits plump over the British Isles. Winds
are light and variable. Once again frost and fog greet us early and
late. An Atlantic LP could send cloud ahead into W Scotland later.

On 21st December, the anticyclone is still with us but spreads E'wards
into the continent. There isn't much change since yesterday. However,
the Atlantic depression is making more headway into NW Scotland, and
here a deterioration in the weather can be expected later.

On 22nd December, the weather has changed. A LP lies to the NW of
Scotland and W winds blow across the N of the country. In the S, a
ridge of HP can be seen in the SW trying to stretch E'wards to the
anticyclone over the continent. To the WSW and S of the country, two
waves can be seen travelling in the direction of the Channel. Probably
the one to the WSW could cause us some trouble later on. The weather
has turned showery in the N half but weather will be dryer in the S.

On 23rd December, a LP centre appears to have moved to SW Norway and
has a trough from Denmark down into Holland. The Holland section of
the trough is most probably the secondary LP mentioned yesterday. So
we have NW winds over the country with rising pressure in the Atlantic
just W of Ireland. Weather will be cooler with showers in the NW
winds. The SW of the country should be dryer.

So there we have it. A mixture of weather, and rather unsettled most
of the time. The Iceland LP always seems to be on hand and only
fleeting glimpses of HP, apart from the two and a half days around
20th December.

This forecast finishes just where my Christmas forecast starts. If
you remember I did a "Comprehensive Christmas Outlook" some time ago
It hasn't lost any quality with time and I wouldn't make any changes to
it if I had to do the forecast again today. So I'll do a repost of it
at a more suitable date later on.

Cheers, Keith



..