The familiar sight of the westerlies roaring in from the Atlantic in early
December again this year is an early hint of the weather pattern that is
likely to prevail later in the winter ...... but it's early days! I have
long believed that the ' crunch' time comes soon after the middle of the
month. If a spell of arctic weather develops at that time, even if it lasts
only a few days,then the chances of a major cold spell after Christmas are
much higher. If you look at the coldest winters since the end of WW 2,
nearly all of them gave a hint of things to come in the weeks leading up to
Christmas. I can think of the Decembers of 1946, 1955, 1962, 1968, 1969,
1978,in 1984 and 1985 the cold spell arrived at Christmas, 1986, and 1990.
The late Colin Finch devised a sort of clue that if, in his part of Surrey,
the temperature failed to reach 38f ( 3.5c) on 4 consecutive days in
December up to Christmas then a cold late-winter was highly likely. If this
clue proved negative( ie no cold spell) a mild winter was almost certain -
this is certainly upheld by events in recent years.

A recent example of Colin's clue came in December 1996 when a cold east wind
spell
developed just before Christmas and January 1997 turned out to be a cold
month. In 2000 the cold weather arrived
at Christmas and January turned out to be a chilly month - by the standards
of recent years.

So many recent years have given what I call a ' phantom cold spell' in mid
December.
.. A high settles over the country in early/ mid December but the air is not
particularly
cold. With clear skies on some nights there are frosts and some fog, but
day temperatures are unremarkable unless the fog lasts all day - as last
year. Then, after a few days, the high moves
away and the westerlies return.

Of course, all these weather theories are fallible, but it's interesting to
speculate and
it will be interesting to see, this year, whether the westerlies suffer a
serious interruption before Christmas.

Peter Clarke
Ewell, Epsom