"John Hall" wrote in message
...
In article ,
Martin Rowley m
writes:
1500 NE F2 4000 HZ 8/ST T-004D-024
RMK: Haze thinning a little; St~010, some character to it but shows
no
sign of breaking. Some light snow (-SN) seen in the vicinity of
Winkfield / North Ascot, but none here - just a few flakes.=

Given how much warmer the air is aloft, that must be precipitating out
from a very low level.


Indeed, the cloud base I estimate was circa 800 ft where I observed the
snow (and this ties in with other reports in the area) and Herstmonceux
12Z would imply cloud has depth circa 60-70 mbar, or approx. 2000ft.
with cloud top temperatures close to MS05C; from empirical studies in
the 1970's and earlier, this is just about on the edge of conditions
likely to produce precipitation - though I have to confess I would have
expected snow *grains* rather than 'proper' snow flakes: I would have
thought the cloud would have had to be colder and deeper for the
processes required to produce flakes? Any cloud physicists care to
comment?

Incidentally, since I posted the original report, I had an email from
Windsor confirming the reports, with at least 20 mins-worth of snow,
giving icy conditions. Quite remarkable.

Martin.