Richard Dixon wrote:

On Wednesday, 10 December 2014 14:24:10 UTC, Stephen Davenport wrote:

It makes a kind of sense because mid Dec-Jan regimes are often linked, so a
cold block, for example, in mid December would more often than not also be
January's characteristic.

This is what I was thinking. Cold air in the UK in December, especially
prolonged cold suggest it's come from the East which in itself implies that
the "East" has cooled down quickly and provide a source of cold and I'd
imagine that a colder East with an existing high pressure/cold pool might be
prone to more stagnation during the remainder of the winter.

Richard

One that perhaps supports your argument in a negative way is Dec 1981 to Feb
1982. Dec 81 was extremely cold in the SE. At Chalfont St Giles the mean daily
max was only 2.8 and there were 6 days with the max below zero. There were 23
days with snow lying at 0900. It would easily have triggered Colin Finch's rule
yet Jan/Feb 82 were rather mild overall, apart from the 2nd week in January
which was cold with a major snowstorm on the 8th.

The cold in Dec 81 was not the result of in incursion of easterly air. If I
recall correctly it resulted mostly from northerly plunges behind lows tracking
SE across the country. It was a very cyclonic month, not what you would
initially think would produce severe cold in December. There was therefore no
pre-existing block to persist into Jan/Feb.


--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
http://peakdistrictweather.org