On Wednesday of last week we had a very uncomfortable day, temperature /
humidity wise.
The weather was also very overcast with several short spells of drizzle
during the day.

I found it strange that the precipitation wasn't heavier taking into account
the cloud thickness.

What causes the differences? was it that there really wasn't any cool enough
air aloft for any heavier precipitation to develop, especially as it was
also fairly breezy.

Any answers anybody?

Thanks.

Len.

"GKN" wrote in message
...
On Wednesday of last week we had a very uncomfortable day, temperature /
humidity wise.
The weather was also very overcast with several short spells of drizzle
during the day.

I found it strange that the precipitation wasn't heavier taking into
account the cloud thickness.

What causes the differences? was it that there really wasn't any cool
enough air aloft for any heavier precipitation to develop, especially as
it was also fairly breezy.

Any answers anybody?

Thanks.

Len.

How thick was the cloud?

Will
--

Hi Will.
I am not sure as to its actual thickness, but it looked at times that it
should have been pouring with rain. Lets say I have seen heavier rain with
the sun shining through thinner cloud.

Im just having a little difficulty understanding the mechanism.
Regards.
Len.
"Will Hand" wrote in message
...

"GKN" wrote in message
...
On Wednesday of last week we had a very uncomfortable day, temperature /
humidity wise.
The weather was also very overcast with several short spells of drizzle
during the day.

I found it strange that the precipitation wasn't heavier taking into
account the cloud thickness.

What causes the differences? was it that there really wasn't any cool
enough air aloft for any heavier precipitation to develop, especially as
it was also fairly breezy.

Any answers anybody?

Thanks.

Len.

How thick was the cloud?

Will
--

On 15 Aug, 21:27, "GKN" wrote:
Hi Will.
I am not sure as to its actual thickness, but it looked at times that it
should have been pouring with rain. Lets say I have seen heavier rain with
the sun shining through thinner cloud.

Im just having a little difficulty understanding the mechanism.


Maybe the freezing level was high and the cloud was mainly water,
rather than having ice crystals?

(GCSE Geography level answer I'm afraid)

"GKN" wrote in message
news
Hi Will.
I am not sure as to its actual thickness, but it looked at times that it
should have been pouring with rain. Lets say I have seen heavier rain with
the sun shining through thinner cloud.

This doesn't answer your question but I have often noticed that
with an approaching front the cloud needs to build up to a
great thickness (based on darkness) before any rain falls
Conversely as the front pulls away there can stil be moderate
rain falling when the sky is really quite bright, even with fleeting
glimples of the sun.
--
Col

Bolton, Lancashire
160m asl

Col wrote:
....
Conversely as the front pulls away there can stil be moderate
rain falling when the sky is really quite bright, even with fleeting
glimples of the sun.

"Glimples" is a lovely word! I shall use it as much as poss from now on.
We get quite a lot of them in Dorset.

Hugh

--

Hugh Newbury

www.evershot-weather.org

"Hugh Newbury" wrote in message
...
Col wrote:
...
Conversely as the front pulls away there can stil be moderate
rain falling when the sky is really quite bright, even with fleeting
glimples of the sun.

"Glimples" is a lovely word! I shall use it as much as poss from now on.
We get quite a lot of them in Dorset.

LOL!
I wonder how on earth I managed that one, given that 's' and 'l'
are on opposite sides of the keyboard!
--
Col

Bolton, Lancashire
160m asl

"Col" wrote in message
...

"GKN" wrote in message
news
Hi Will.
I am not sure as to its actual thickness, but it looked at times that it
should have been pouring with rain. Lets say I have seen heavier rain
with the sun shining through thinner cloud.


For proper rain as opposed to drizzle you need upward motion and the correct
microphysics within the cloud. Either enough moisture to produce raindrops
by coalescence or (more normally in UK) the presence of ice crystals.
Thinnish altostratus with sun visible will produce rain as the air is
ascending normally due frontal ascent and there are ice crystals allowing
rain production by the Bergeron Findeisen process, i.e. tiny water cloud
droplets evaporate and condense onto ice crystals eventually falling out as
snow then melting to give rain. In mountain terrain thinnish stratus or
stratocumulus cloud can produce copious rainfall if very moist air is
continually lifted over the high ground and the stratus clouds are seeded
with rainfall/snow from above. So I hope you can see that optical thickness
(darkness) of clouds is not always the best guide as to what clouds will
give a lot of rain, one has to understand the physics and cloud dynamics as
well!

HTH

Cheers,

Will
--

Well thank you all for your replies, from your answers I can see that its
not as simple as I first thought, oh well back to the drawing board.

Thanks again and best regards.

Len.

"Will Hand" wrote in message
...

"Col" wrote in message
...

"GKN" wrote in message
news
Hi Will.
I am not sure as to its actual thickness, but it looked at times that it
should have been pouring with rain. Lets say I have seen heavier rain
with the sun shining through thinner cloud.


For proper rain as opposed to drizzle you need upward motion and the
correct microphysics within the cloud. Either enough moisture to produce
raindrops by coalescence or (more normally in UK) the presence of ice
crystals.
Thinnish altostratus with sun visible will produce rain as the air is
ascending normally due frontal ascent and there are ice crystals allowing
rain production by the Bergeron Findeisen process, i.e. tiny water cloud
droplets evaporate and condense onto ice crystals eventually falling out
as snow then melting to give rain. In mountain terrain thinnish stratus or
stratocumulus cloud can produce copious rainfall if very moist air is
continually lifted over the high ground and the stratus clouds are seeded
with rainfall/snow from above. So I hope you can see that optical
thickness (darkness) of clouds is not always the best guide as to what
clouds will give a lot of rain, one has to understand the physics and
cloud dynamics as well!

HTH

Cheers,

Will
--