Re: A real Battleground!!

On 29 Dec, 11:39, robkings...@xxxxxxxxx wrote:
On Dec 29, 9:58 am, crazyh0r...@xxxxxxxxxxx wrote:

Given that the increasing amounts of traffic and urban sprawl have
raised average temperatures by a degree or so over the last 50 years
in southern parts (especially night minima), it has probably made a
really decent snowfall in the south much more unlikely, given that 1
deg C can make the difference in many areas between a snowy landscape
and 24 hours of sleet/rain.

Do you have any evidence to back that up? I find itr very hard to
believe that "traffic and urban sprawl" have anything more than a very
local effect (the urban heat island). Certainly claiming a 1C rise
over the whole of southern England seems a little extreme. In the
centre of towns perhaps, but not out in the sticks...

Nope. no evidence at all.

But it depends on how you want to define southern England. There is
not much that I would describe as 'in the sticks' between Kent/Essex
and Hampshire/Berkshire/Oxfordshire. In the majority of snow
situations, and I'm really thinking of weather fronts from the
southwest becoming slow moving against a cold easterly flow, the
surface winds will generally from the east.

If that wind is travelling over an increasingly urbanised area, then
it will be warmed very slightly by that progress. The effect may only
be one degree, but in many snow/sleet/rain situations that would be
enough.

As for 'the urban heat island', I would venture to suggest that it has
now expanded to almost a 50 mile radius from central London. That is a
rather large island.

In December 1981, a deepening low pressure area moved east almost up
the Bristol Channel. In Bristol and the surrounding area, there was a
blizzard and the region was almost cut off for a few days. There was a
near easterly gale ahead of the low, which added to the severe
drifting. In Cardiff there may have been a few hours of wet snow,
followed by lots of rain. The gale force easterlies could have only
spent about 30 minutes crossing the Bristol Channel between the two
cities, but that would seem to be the reason for the difference in
weather conditions only 25 miles apart.

My point is, that there is such a fine line around the snow/rain
weather boundary that almost imperceptable differences may be enough
to tip the balance.
.

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