Visible to the south east after 0800 today. Only a small patch but the first
I've seen for some time.

--
David Mitchell, 70m amsl, Langtoft, East Riding of Yorkshire.

On a tatty piece of sub-ether David Mitchell at said...
Visible to the south east after 0800 today. Only a small patch but the first
I've seen for some time.


Certain you got the right one mate? Easy to get confused with iridescent
cloud....

http://en.wikipedia.org/wiki/Nacreous_cloud
http://www.psi.edu/iridescent.html
--
Rob C. Overfield
Hull

On Feb 1, 9:14 pm, "David Mitchell" wrote:

Visible to the south east after 0800 today. Only a small patch but the first
I've seen for some time.

Are you sure it wasn't iridisation in some high cirrus?

It is the right time of year for them so it may have been a display.

I didn't see it. Did anyone get photographs of them? That would be
helpful.
Can anyone confirm if they were in fact lenticular stratospheric
nacreous clouds?
They do have a very aerodynamic wind swept characteristic shape.

Some pictures from the big display of 1996 on my webpage (together
with a list of all known UK displays for the past century)

http://www.nezumi.demon.co.uk/nacreous/nacreous.htm

They form usually at such a high altitude as to be visible over a very
wide area.

Regards,
Martin Brown

"Martin Brown" wrote in message
oups.com...
On Feb 1, 9:14 pm, "David Mitchell" wrote:

Visible to the south east after 0800 today. Only a small patch but the
first
I've seen for some time.

Are you sure it wasn't iridisation in some high cirrus?

It is the right time of year for them so it may have been a display.

I didn't see it. Did anyone get photographs of them? That would be
helpful.
Can anyone confirm if they were in fact lenticular stratospheric
nacreous clouds?
They do have a very aerodynamic wind swept characteristic shape.

Some pictures from the big display of 1996 on my webpage (together
with a list of all known UK displays for the past century)

http://www.nezumi.demon.co.uk/nacreous/nacreous.htm

They form usually at such a high altitude as to be visible over a very
wide area.

Regards,
Martin Brown


Thanks for the reply guys and I can assure you it was a single small cloud.
(I was driving south, so guess there could have been some behind me). You
had me doubting myself and I had to check out cloud sites to confirm it to
myself, but anyone who witnessed/photographed 1996 won't forget them.
Martin your description "bright white" sums it up quite well, it was very
bright. Can't think why I didn't stop and photograph it.


--
David Mitchell, 70m amsl, Langtoft, East Riding of Yorkshire.

On Fri, 2 Feb 2007 18:07:01 -0000, David Mitchell wrote:

Visible to the south east after 0800 today. Only a small patch but
the first I've seen for some time.

Are you sure it wasn't iridisation in some high cirrus?

Thanks for the reply guys and I can assure you it was a single small
cloud.

But surely at 0800 the sun is above the horizon. IIRC you only see
nacreous cloud when the sun is below the horizon.

--
Cheers
Dave. pam is missing e-mail

But surely at 0800 the sun is above the horizon. IIRC you only see
nacreous cloud when the sun is below the horizon.

--
Cheers
Dave. pam is missing e-mail

Interesting point. Googled it and the first response was from dear old Bill
Giles on the BBC site. "Both are rare clouds and can only be seen, briefly,
at sunrise and sunset when all the other lower clouds are in shadow." Just
checked our sunrise time for today and its 0748. How long they last after
sunrise I couldn't say - but I saw it. I couldn't honestly say what the
exact time was, other than I left home before 0800 and observed it within a
couple of minutes from the Wolds top.

--
David Mitchell, 70m amsl, Langtoft, East Riding of Yorkshire.

On Fri, 2 Feb 2007 23:44:54 -0000, David Mitchell wrote:

But surely at 0800 the sun is above the horizon. IIRC you only see
nacreous cloud when the sun is below the horizon.

Interesting point. Googled it...

So did I and found a few references to the sun being something like 5 to
10 degrees below the horizon. Now 5 degrees is 20 mins with sun coming
straight up. It will be longer with the sun rising at an angle.

As it was small patch could it have been a sun dog?

--
Cheers
Dave. pam is missing e-mail

"Dave Liquorice" wrote in message
ll.com...
On Fri, 2 Feb 2007 23:44:54 -0000, David Mitchell wrote:

But surely at 0800 the sun is above the horizon. IIRC you only see
nacreous cloud when the sun is below the horizon.

Interesting point. Googled it...

So did I and found a few references to the sun being something like 5 to
10 degrees below the horizon. Now 5 degrees is 20 mins with sun coming
straight up. It will be longer with the sun rising at an angle.

As it was small patch could it have been a sun dog?

--
Cheers
Dave. pam is missing e-mail


Thanks for the suggestion Dave.
I don't believe it was a sun dog. It was a genuine patch of bright cloud,
and a high one! When I say small it was significantly larger than a sun dog,
but one isloated cloud.
As I travelled south then south west over a couple of miles, the cloud took
on the distinctive look of a nacreous cloud, presumably with the change in
angle.
I'll stand by my original report, until an alternative option is given that
I can relate to!!

--
David Mitchell, 70m amsl, Langtoft, East Riding of Yorkshire.

On Feb 2, 11:04 pm, "Dave Liquorice" wrote:
On Fri, 2 Feb 2007 18:07:01 -0000, David Mitchell wrote:
Visible to the south east after 0800 today. Only a small patch but
the first I've seen for some time.

Are you sure it wasn't iridisation in some high cirrus?

Thanks for the reply guys and I can assure you it was a single small
cloud.

But surely at 0800 the sun is above the horizon. IIRC you only see
nacreous cloud when the sun is below the horizon.

There are a few reliable reports of nacreous clouds (particularly the
slightly denser lenticular ones that appear "bright white" with green-
red pastel interference fringes at the edge) being seen with the sun
*just* above the horizon. The highly coloured ones though are
virtually transparent and disappear very quickly at sunrise (I have
never seen them in the morning myself).

http://www.meteo.be/english/index.php?doc=OzonEN

The ozone level over Uccle in Belgium (real time graph) shows a slight
dip recently, but not a major collapse as would be expected if there
had been a significant region with PSCs forming in the stratosphere.

AFAIK there is only one fully daytime observation of nacreous? clouds
in 1951 August 10 1230-1330 (an unusual date too - most UK displays
are seen in winter). He was only able to see the cloud after climbing
to above 30000 feet. This particular observation was made by a test
pilot in experimental British jet aircraft who flew through a nacreous
cloud and reported it as being at extremely high altitude located
between 46500 and 47500 feet and optically thin. The air temperature
in the cloud was measured as -56C (which sounds about 20 degrees too
warm for PSCs to me) The pilot remarked that in his entire career he
had never before seen any clouds above 42000 feet whilst testing
aircraft up to 50000ft. I believe this one summer observation is
unique in the UK.

The pilot is not named, but the anonymous report is "Very high cloud
layer, August 10 1951", Meteorological Magazine, 80, p365-6.

Regards,
Martin Brown

"Martin Brown" wrote in message
ps.com...
On Feb 2, 11:04 pm, "Dave Liquorice" wrote:
On Fri, 2 Feb 2007 18:07:01 -0000, David Mitchell wrote:
Visible to the south east after 0800 today. Only a small patch but
the first I've seen for some time.

Are you sure it wasn't iridisation in some high cirrus?

Thanks for the reply guys and I can assure you it was a single small
cloud.

But surely at 0800 the sun is above the horizon. IIRC you only see
nacreous cloud when the sun is below the horizon.

There are a few reliable reports of nacreous clouds (particularly the
slightly denser lenticular ones that appear "bright white" with green-
red pastel interference fringes at the edge) being seen with the sun
*just* above the horizon. The highly coloured ones though are
virtually transparent and disappear very quickly at sunrise (I have
never seen them in the morning myself).

http://www.meteo.be/english/index.php?doc=OzonEN

The ozone level over Uccle in Belgium (real time graph) shows a slight
dip recently, but not a major collapse as would be expected if there
had been a significant region with PSCs forming in the stratosphere.

AFAIK there is only one fully daytime observation of nacreous? clouds
in 1951 August 10 1230-1330 (an unusual date too - most UK displays
are seen in winter). He was only able to see the cloud after climbing
to above 30000 feet. This particular observation was made by a test
pilot in experimental British jet aircraft who flew through a nacreous
cloud and reported it as being at extremely high altitude located
between 46500 and 47500 feet and optically thin. The air temperature
in the cloud was measured as -56C (which sounds about 20 degrees too
warm for PSCs to me) The pilot remarked that in his entire career he
had never before seen any clouds above 42000 feet whilst testing
aircraft up to 50000ft. I believe this one summer observation is
unique in the UK.

The pilot is not named, but the anonymous report is "Very high cloud
layer, August 10 1951", Meteorological Magazine, 80, p365-6.

Regards,
Martin Brown


Is it fair to suggest that there is some doubt in my observation?
I can only report what I saw and relate it to what I have seen on other
occassions.


--
David Mitchell, 70m amsl, Langtoft, East Riding of Yorkshire.