On Wed, 12 Aug 2015 15:29:05 +0100
"Eskimo Will" wrote:


"Stephen Davenport" wrote in message
...
On Wednesday, August 12, 2015 at 10:10:58 AM UTC-4,
wrote:
"Stephen Davenport" wrote in message
...
On Wednesday, August 12, 2015 at 9:17:11 AM UTC-4, Asha Santon
wrote:
I just made a new photo to replace an old one made by dear mama.

Could some kind person tell me what type of cloud this is?
http://pictures.opcop.org.uk/new99.htm

The sky is full of this type just now and if I know what it is,
I can change the title on the page.
If there's somewhere I can look such things up to avoid
bothering the ng
please do tell.

Thanks in anticipation of someone being nice

========

Altocumulus stratiformis translucidus perlucidus.

Or, given that it is difficult to gauge altitude from a
photograph, possibly high stratocumulus.



Probably Ac I'd say.


Yes, I think so. It immediately looks like Ac but I couldn't
entirely rule out Sc.


Indeed not. Even outside height can be deceptive. I remember one
night shift way back in the 70s as a trainee observer; it was around
dawn and I said to my colleague that there was a bit of stratus
outside. He immediately corrected me and said I don't think so, that
is cirrus s****atus at around 20000 feet! Only 19500 feet out. Air
traffic control would not have been pleased if I had reported patchy
stratus. I was fooled by the fact that the cirrus showed up dark and
was moving quite fast. The CBR was no help (it would not have
recorded cirrus) as the cloud was not over it. When the sun came up,
my error became obvious :-)


While we're on the subject of Ac, I remember seeing a typical "mackerel
sky" one evening about fifty years ago. Typical apart from it being in a
field at about half-a-dozen feet above the ground. I think it may have
been raining earlier and then the sky cleared. I only recently thought
how it had formed and I reckon cold air had rolled down the slope of the
field into a clump of trees at the bottom. A flow of air from the
trees then rolled up the hill creating turbulence at the interface of
the two flows. "Cloud", no more than a foot thick, then formed in the
turbulent layer.

I've seen Ci thicken and darken until it blotted out the sun, having
gone through the As stage where the sun could be seen weakly as through
ground glass. It then developed large, black, ragged rolls like Sc or
St at 800-1,000ft. An aircraft reported the base at 25,000ft with top
34,000.

Nearly fifty years ago, there were reports from Australia of Sc that
was estimated at 4,000ft that turned out to be at 25,000ft. One Sunday
lunchtime, a few weeks after seeing those reports, I saw some Ci Spi
change into what looked like separate Sc or shallow Cu cells at what
might have been estimated to be as low as 3,000ft.

There are more instances of where height estimates by experienced
observers have been out by an order of magnitude, either too low or too
high.

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
Posted with Claws: http://www.claws-mail.org/

"Stephen Davenport" wrote in message
...
On Wednesday, August 12, 2015 at 10:29:13 AM UTC-4,
wrote:
"Stephen Davenport" wrote in message
...
On Wednesday, August 12, 2015 at 10:10:58 AM UTC-4,
wrote:
"Stephen Davenport" wrote in message
...
On Wednesday, August 12, 2015 at 9:17:11 AM UTC-4, Asha Santon wrote:
I just made a new photo to replace an old one made by dear mama.

Could some kind person tell me what type of cloud this is?
http://pictures.opcop.org.uk/new99.htm

The sky is full of this type just now and if I know what it is, I
can
change the title on the page.
If there's somewhere I can look such things up to avoid bothering
the
ng
please do tell.

Thanks in anticipation of someone being nice

========

Altocumulus stratiformis translucidus perlucidus.

Or, given that it is difficult to gauge altitude from a photograph,
possibly high stratocumulus.



Probably Ac I'd say.


Yes, I think so. It immediately looks like Ac but I couldn't entirely
rule
out Sc.


Indeed not. Even outside height can be deceptive. I remember one night
shift
way back in the 70s as a trainee observer; it was around dawn and I said
to
my colleague that there was a bit of stratus outside. He immediately
corrected me and said I don't think so, that is cirrus s****atus at around
20000 feet! Only 19500 feet out. Air traffic control would not have been
pleased if I had reported patchy stratus. I was fooled by the fact that
the
cirrus showed up dark and was moving quite fast. The CBR was no help (it
would not have recorded cirrus) as the cloud was not over it. When the sun
came up, my error became obvious :-)


==============

Observing at night often presented these kinds of problems.

At London Weather Centre the issue was exacerbated by light pollution.
Oftentimes one would have merrily reported clear skies on the hour through
the night only to be confronted by several oktas of thin high cirrus at
dawn - which may or may not have present previously.

There was an article written a few years ago which made a case for
mechanisms that caused dispersal of cirrus overnight; but I wondered if the
author missed the simple point that it's simply a bugger to see at night.

As for lower cloud, we had one observer for a while who seemed only ever to
observe two stratiform types - Sc at 2500' or St at a peculiarly high 2000'.
In a westerly it was wise to at least look at what upstream sites with CBRs
were reporting, especially LHR. He never caught on.

===========

Ah yes the night-time cirrus riddle. I'm sure you are spot on Stephen. I was
taught that you had to spend at least 5 minutes outside to get used to the
reduced light. Then you needed to see how many stars were blotted out, more
difficult with human lights around as on an airfield. In the end I was told
if in doubt report 3/8 Ci type 1. That usually worked!

At Finningley I made a huge boo boo due to a lot of lights around. I had
been reporting 5/8 Ci most of the night, but as dawn came up to my horror it
became obvious that there was a very thin stratus deck at around 800 feet.
Naturally that suddenly formed around dawn :-) Luckily it was a weekend with
no flying and the CBR was off and I didn't bother with the searchlight, why
would you with just cirrus. teleprinters were off too, so had no idea what
others were reporting.

As for getting night vision, well that did sometimes interrupt the game of
cards on a night shift at Manby. Bruce will know about all that stuff :-)

This reminiscing is making me feel *very* old!

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

If my memory serves me correctly, CBRs in the early 70s only recorded up to 4000ft.

On Wed, 12 Aug 2015 08:42:46 -0700 (PDT)
Desperate Dan wrote:

If my memory serves me correctly, CBRs in the early 70s only recorded
up to 4000ft.

That's true, we had one at Wyton for evaluating when I joined in '62. At
nighttime, however, we could use Alconbury's searchlight to get the
height of cirrus!

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
Posted with Claws: http://www.claws-mail.org/

"Graham P Davis" wrote in message
news:20150812180458.21992393@linux-is7a...
On Wed, 12 Aug 2015 08:42:46 -0700 (PDT)
Desperate Dan wrote:

If my memory serves me correctly, CBRs in the early 70s only recorded
up to 4000ft.

That's true, we had one at Wyton for evaluating when I joined in '62. At
nighttime, however, we could use Alconbury's searchlight to get the
height of cirrus!

--
Graham P Davis, Bracknell, Berks. [Retd meteorologist/programmer]
http://www.scarlet-jade.com/
I wear the cheese. It does not wear me.
Posted with Claws: http://www.claws-mail.org/



Well Graham, that reminds me...

I was at Wyton in 1958, and used to take aledade readings on the Alconbury
searchlight too. When I first noticed the spot on distant clouds to the west
I contacted the USAF there, and they kindly provided me with the
co-ordinates of the searchlight. If I remember correctly, the baseline to
Wyton was around 10 km. They used an arc-lamp that produced a very intense
beam, from which cloud heights of up to about 25000 ft could be obtained
from Wyton. At Alconbury they probably measured the height electronically,
as I later saw a similar type of American arc-lamp searchlight at Aberporth
that displayed to cloud height on a CRT.

--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
http://www.woksat.info/wwp.html



---
This email has been checked for viruses by Avast antivirus software.
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On 12/08/2015 14:16, Asha Santon wrote:
I just made a new photo to replace an old one made by dear mama.

Could some kind person tell me what type of cloud this is?
http://pictures.opcop.org.uk/new99.htm

-------------------------------------------------------------
Would love to help Asha but .....

I've looked at clouds from both sides now
From up and down and still somehow
It's cloud illusions I recall
I really don't know clouds at all.
Dave

On 12/08/2015 15:11, Stephen Davenport wrote:
On Wednesday, August 12, 2015 at 9:17:11 AM UTC-4, Asha Santon wrote:
I just made a new photo to replace an old one made by dear mama.

Could some kind person tell me what type of cloud this is?
http://pictures.opcop.org.uk/new99.htm

The sky is full of this type just now and if I know what it is, I can
change the title on the page.
If there's somewhere I can look such things up to avoid bothering the ng
please do tell.

Thanks in anticipation of someone being nice

========

I should add, by the way, that altocumulus is the genus, stratiformis the species (meaning, as the word suggests, an extensive layer).

Translucidus and perlucidus are varieties: the former, also easily guessed, meaning translucent - such that the sun or moon may be seen through the cloud. Thick altocumulus is the variety opacus. Perlucidus is less obvious but denotes gaps between cloud cells in the layer. Literally it means something like "allowing light through".

Stephen.


Isn't perlucidus bit not needed, I always think of Ac as cow pats in the
sky.

On 2015-08-12 18:15:35 +0000, Dave Cornwell said:

On 12/08/2015 14:16, Asha Santon wrote:
I just made a new photo to replace an old one made by dear mama.

Could some kind person tell me what type of cloud this is?
http://pictures.opcop.org.uk/new99.htm

-------------------------------------------------------------
Would love to help Asha but .....

I've looked at clouds from both sides now
From up and down and still somehow
It's cloud illusions I recall
I really don't know clouds at all.
Dave

I had to look that up and I think this must be it
https://en.wikipedia.org/wiki/Both_Sides,_Now

Ancient music
I was just the right age (12) when the girls came along and told me
what I want, what I really, really want ...

--
AS
http://minnies.opcop.org.uk
I knew the Triffids were real when I saw the signs
Caution: Heavy plant crossing

On Wednesday, August 12, 2015 at 7:15:39 PM UTC+1, Dave Cornwell wrote:
On 12/08/2015 14:16, Asha Santon wrote:
I just made a new photo to replace an old one made by dear mama.

Could some kind person tell me what type of cloud this is?
http://pictures.opcop.org.uk/new99.htm

-------------------------------------------------------------
Would love to help Asha but .....

I've looked at clouds from both sides now
From up and down and still somehow
It's cloud illusions I recall
I really don't know clouds at all.
Dave
================================================== ===================
Surely you know S****atus Dave?
;-)

Len
------------------------------------------------------------------------

On Wednesday, 12 August 2015 16:42:47 UTC+1, Desperate Dan wrote:
If my memory serves me correctly, CBRs in the early 70s only recorded up to 4000ft.

Yes you are correct.

The cloud base recorder was typical Met Office - designed by someone with an elecronics background and neither an observer or a forecaster. The chart was no more than 3x3" window in a large box (18x12" approx) of valves and circuits, it even had some kind of meter that was as big as the chart that recorded the cloud base!

Around the same time there was a visiometer that output to a Kent chart recorder which is probably what the CBR should have employed and would have been a lot more useful. I bet that came from outside the Office.

It's sad but I can still remember how it sounded as the arm moved up the chart...

Wasn't there a paper on the dispersal of night time cirrus at daybreak?