.... well, not quite, but on my walk to get the paper (~0830GMT/9.30am
local), one of those oddities of the weather - definite shower of rain
coming straight down, with no 'parent' cloud apparent overhead.

At the time, the sky was a mix of dense Cirrus, some flat-looking Ac
(might scrape an eighth out of it), and any Cu was very distant. I was
well away from trees (in any case the wind not strong enough to drive
droplets off the branches / leaves) and no sign of a decaying Cu to
account for the shower. Not just a few droplets either, but enough for
drivers on the Crowthorne Road to put wipers on!

I suspect that, given the high relative humidity at the moment, the
shower was due to a low-base Ac cas (of which there are some around now~
base 7000-8000ft) drifting overhead from the SSE, which had long since
moved on, but left it's product of large rain drops to fall without
evaporating significantly.

Anyone got any other ideas?

Martin.


--
Martin Rowley: data via -
http://homepage.ntlworld.com/booty.weather/metindex.htm
Bracknell (Wooden Hill/Tawfield), Berkshire
NGR: SU 854 667 Elev: 80m
Lat: 51DEG23MIN30SEC(N): Long: 00DEG46MIN28SEC(W)

Anyone got any other ideas?

Strange you have mentioned this. I have wondered about this very thing
for a number of years now. Not just rain, but also snow!

Simon

"Simon Wyndham" wrote in message
...

Strange you have mentioned this. I have wondered about this very thing
for a number of years now. Not just rain, but also snow!

.... yes, I've seen the same thing with snow, though usually the 'parent'
cloud is more obvious - I suspect the common feature is the highly
sheared environment (at least it was this morning), the reasonably high
relative humidity and the high degree of instability, enabling a
'collection' of droplets to be slowed down on their descent towards
earth (against the buoyancy of the strong upward dry thermals) with the
cloud generating the PPN moving on (or dispersing) as the PPN fights its
way earthward: only a theory though.

Martin.

--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm
and
http://booty.org.uk/booty.weather/metindex.htm

In article ,
Simon Wyndham writes:

Anyone got any other ideas?

Strange you have mentioned this. I have wondered about this very thing
for a number of years now. Not just rain, but also snow!

Snow is easier to understand, as one can imagine snowflakes being
carried a considerable distance on the wind.
--
John Hall
Johnson: "Well, we had a good talk."
Boswell: "Yes, Sir, you tossed and gored several persons."
Dr Samuel Johnson (1709-84); James Boswell (1740-95)

Martin Rowley wrote:
"Simon Wyndham" wrote in message
...

Strange you have mentioned this. I have wondered about this very thing
for a number of years now. Not just rain, but also snow!

... yes, I've seen the same thing with snow, though usually the 'parent'
cloud is more obvious - I suspect the common feature is the highly
sheared environment (at least it was this morning), the reasonably high
relative humidity and the high degree of instability, enabling a
'collection' of droplets to be slowed down on their descent towards
earth (against the buoyancy of the strong upward dry thermals) with the
cloud generating the PPN moving on (or dispersing) as the PPN fights its
way earthward: only a theory though.

Snow is the product of sheep shearing?

Baa'a!

What happened to that thread a couple of years or so back about rain in
the middle of an high? As it happens all bets are off with the scale of
this year's NOA.. It is an interesting time.

Simon Wyndham wrote:
Anyone got any other ideas?

Strange you have mentioned this. I have wondered about this very thing
for a number of years now. Not just rain, but also snow!

Simon

This reminds me of an event a few years ago. I was sitting out in my
back garden just watching swifts against a backdrop of dense Cirrus. A
small patch of Ac floated by which looked a little lumpy but you could
not call it castellanus. There was no other cloud. After about 3
minutes there was a sudden shower of large rain spots which lasted
around 90 seconds. By that time the Ac had vanished, and the sky
contained nothing but Cirrus.

John Hall wrote:

In article ,
Simon Wyndham writes:

Anyone got any other ideas?

Strange you have mentioned this. I have wondered about this very thing
for a number of years now. Not just rain, but also snow!

Snow is easier to understand, as one can imagine snowflakes being
carried a considerable distance on the wind.

It's nothing to do with wind. What usually happens is that snow starts
falling from a cloud and then the whole cloud dissolves into snow. So
before the snow reaches the ground - or rain, if the snow melts - the cloud
has vanished. When I was a child, I noticed this effect was most common
during the early morning. At this time of day, there seems to me to be a
peak of shower activity associated with showers advected inland. As local
convection hasn't started, once the cloud starts precipitating, there's no
mechanism for regenerating the cloud.

You can see precipitation falling through the sky, with no sign of the
source cloud, on many days of the year. Most cirrus that you see is not
really cloud, it's precipitation, and the originating cloud has long gone.

--
Graham Davis
Bracknell