"Gavin Staples" wrote in message
...
This would cause the high to pull a wedge of cold air from NW Russia
in our direction.
An excellent explaination.
I sometimes use the phrase "cold pool" in my analysis to indicate such a
pool moving across the UK.
In fact (at the time of writing) the 12z GFS run shows this in action:
http://129.13.102.67/wz/pics/Rtavn001.gif
Have a look near the Balkans - there's currently a pool of colder air over
there, which would have come about before the Scandinavian and Siberian
Highs linked.
It then tracks westwards over France...
http://129.13.102.67/wz/pics/Rtavn121.gif
http://129.13.102.67/wz/pics/Rtavn361.gif
By T+36, a new ridge NE of Scandinavia allows another cold plunge of air to
head southwards.
http://129.13.102.67/wz/pics/Rtavn601.gif
Sunday sees the first cold pool finally make it across the Channel, as it's
pushed NW'wards around the high.
Meanwhile low pressure moves southwards over NW Russia as a ridge topples
southwards and by T+72 the greens start moving towards eastern Europe,
heralding another cold pool.
http://129.13.102.67/wz/pics/Rtavn721.gif
By now, the first cold pool moves over Scotland, cooling further as it moves
back northwards again.
There are also signs of yet another ridge between Scandinavia and
Greenland - if the high remained in situ, you'd see cold pools circling it,
like the teeth of a cog rotating.
Finally, by T+96 our cold pool merges with the cooler air north of Iceland,
while the cold NE'ly flow over NW Russia gets cut off, with a cold pool
heading over the Black Sea:
http://129.13.102.67/wz/pics/Rtavn961.gif
Of course, this is pretty tame stuff - that cold pool will reduce
temperatures by a few degrees, but for a wintry cold pool, you can't really
beat January 1987:
http://217.160.130.220/wz/pics/archi...0119870106.gif
http://217.160.130.220/wz/pics/archi...0119870108.gif
http://217.160.130.220/wz/pics/archi...0119870110.gif
http://217.160.130.220/wz/pics/archi...0119870112.gif
http://217.160.130.220/wz/pics/archi...0119870114.gif
http://217.160.130.220/wz/pics/archi...0119870115.gif
High pressure moving over the UK then merging with a high originally to the
east of Svalbard, with an intense cold pool pushed towards and eventually
over the UK, warming considerably as it did so - but not by enough to stop
it being an exceptionally cold spell of course.