"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)
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