"nguk." wrote in message
...
I don't know how to word this correctly but here goes
How does a cold pool come about and what sort of temps can be expected if
one arrives here this month?




This is an excellent question:


It is quite straightforward really. That is assuming my description is
correct. A cold pool forming from a high pressure system is created soon
after an intensification of the high pressure to the east or north east of
the UK. This would cause the high to pull a wedge of cold air from NW Russia
in our direction. This cold pool would accumulate over the UK until the high
pressure weakened sufficiently to allow warmer west or sw winds to remove
it. In rare occasions the cold pool would sit until it was reinvigorated by
a resurgence of the high or even a shift in the high pressure to an even
more advantageous position.
In most cases though the cold pool will sit until the air warms in its
lower altitudes giving a few good night frosts until such time as the high
declines and then the cold pool is replaced by milder air.
The sort of temperatures I would expect in a cold pool over S and
Eastern England in mid November would be daytime maximums of 5C or 6C and
nightime temps of -2C to -3C.
I hope my answer is OK.

Regards, Gavin.


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Regards, Gavin.


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Gavin Staples.

website updated regularly
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Thankyou for your time in writing that
it was most helpful!

"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.

The point about a cold pool, whatever its origin, is that the air is cold
over a considerable depth. The effect of this is to enhance any convection
that may occur. In summer, possibly thunderstorms, in winter maybe snow
showers. In winter low surface temperatures can occur (in a High) with no
trace of a cold pool anywhere near, due to a strong surface inversion, even by
day.

Tudor Hughes, Warlingham, Surrey.