On Fri, 17 Apr 2015 12:20:57 -0700 (PDT)
Tudor Hughes wrote:

On Friday, 17 April 2015 17:39:15 UTC+1, Graham P Davis wrote:
On Fri, 17 Apr 2015 09:26:43 -0700 (PDT)
Tudor Hughes wrote:

On Thursday, 16 April 2015 18:16:01 UTC+1, Graham P Davis wrote:
Picture of beautiful K-H clouds over Essex.

http://www.bbc.co.uk/weather/feature...e=news_central
Spotted this when it was tweeted by Steph Ball a few minutes
ago.


Nice, but I strongly suspect a hoax. The conditions for
K-H waves are simply not there. The Herstmonceux ascent for 12Z
15th April shows very little wind shear. Also, the humdity is
too low.

http://weather.uwyo.edu/cgi-bin/soun...512&STNM=03882

Tudor Hughes, Warlingham, Surrey.


You think the 20kt shear in the moist layer at 350hPa is
insufficient?


No, not in itself but these clouds are not at 350 mb, which
is about 28000 ft. From their texture I'd say they were at less than
half that. Also, the camera angle is low and if they were at 28000
ft they would have to be at a vast distance and they certainly don't
give that impression. There was a lot of haze that day but at cloud
level there looks to be very little. There is no serious wind shear
below 350 mb. Intriguing, but I'm highly suspicious.


I don't see how you can say for certain that these clouds are not at
350hPa though I agree that, in the photo, they look lower. Appearance
is usually a good guide but can be horribly misleading. Nearly fifty
years ago, there was an article (in Weather or Met Mag) about observers
in Australia who'd reported Sc at 4,000ft and been shocked to get
aircraft reports that the base was at 25.000ft. Several "experts" in
the office thought it was down to incompetent Aussie observers but I
was lucky enough a few weeks later to see this phenomena develop where
Ci Spi turned itself into Sc. At the time I hadn't been able to see how
a cloud of ice crystals could turn itself into a water-droplet cloud.
However, about fifteen years ago, I saw how it must have happened.
Vertical plumes of Ci began to develop dark masses near the lower
parts. I realised this must be water-droplet cloud forming in a moist
layer cooled by the ice-crystals falling through it. The most extreme
example of misleading cloud I've seen consisted of dark, charcoal-grey
rolls with ragged bases that looked like St at 800ft. Actually, the
base was 25,000ft with top 34,000!

Another thing to consider is what sort of photo this is. With no
scenery, it's impossible to get an idea of scale; the clouds could be
very small but magnified to make the picture.

Not sure what you're getting at regarding it being hazy that day but
there being none at cloud level. If the cloud were high, there
probably wouldn't be any haze there. There seems to be some haze below
the cloud though.

Of course, we're also at the mercy of the dismal radio-sonde coverage
these days and so it's quite possible that Herstmonceux is not
representative of the airmass over Essex. Even with the coverage we
had forty years ago, I recall a line of thunderstorms occurring where
no ascent gave a cat-in-hell's chance of any convection getting above
10,000ft.

As someone whose had my weaher observations disbelieved by people who
weren't there, I supposed I'm biased in favour of the photographer
here. I don't see any strong evidence for chicanery here.


--
Graham P Davis, Bracknell
Anti-intellectualism has been a constant thread winding its way through
our political and cultural life, nurtured by the false notion that
democracy means that 'my ignorance is just as good as your knowledge.'
- Isaac Asimov.