Hi all,

I wonder if anybody could offer some advice on contrail observation?
When conditions are right and contrails are long lasting and spread
out to lead to Cs or Ci layers do they cease to be contrails for the
purpose of cloud classification and reporting? For example, on a day
with no naturally formed cirriform clouds but with contrails that
develop into a 3 okta Cs/Ci cloud cover should this be recorded as 3Ci
or 3Cs along with a RMK that they evolved from contrails, or is it the
case of once a contrail, always a contrail and a RMK made along the
lines of "Extensive contrails, spreading to form Cs/Ci" with no
comment made upon the extent of cloud cover? I observe many contrails
being situated under several flight paths. I would be very grateful
for some guidance on how one should classify and report man made
cirriform.

Many thanks,

Ian,

Raunds, East Northants. 63m. Grid Ref SP9972
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Ian - the standard practice is to count them as any other cloud for
extent (i.e. cloud cover in oktas) and to show the cloud type as
'cotra' where they are clearly contrails, or 'Ci (or Cs) ex cotra'
where they have evolved into that type.

When they are extensive and persistent it may not be obvious which are
'ex cotra' and which are natural clouds that would have been there
anyway, but the 'ex cotra' or 'partly ex cotra' tag can be added where
the development has been observed to be from contrails even if they
are no longer clearly recognisable as such, or where they may be only
partly from cotra.

The important thing is that they are counted as cloud cover. I can
recall in my Met Office days one auxiliary reporting site (that shall
remain nameless) that for some reason appeared to believe that
contrails were not to be reported as cloud often showing clear skies
(N=0) when all the neighbouring stations would show Ci/Cs, sometimes
6-7/8. Bizarre.

HTH.

Stephen Burt
Stratfield Mortimer, Berkshire

Ian, I do not know if there is any official rulings about this subject, but
personally I report COTRA as a remark if any of the observed cirrus is of
identifiable aircraft origin. There are not many occasions in this area,
there being many overflying jets, that the is doubt or ambiguity about
whether to report COTRA. Contrail cirrus counts towards cloud amount in an
observation, and contributes towards an assessment of the cloud type for
coding purposes.

--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:
www.woksat.info/wwp.html
or
www.btinternet.com/~wokingham.weather/wwp.html
"Ian" wrote in message
ps.com...
Hi all,

I wonder if anybody could offer some advice on contrail observation?
When conditions are right and contrails are long lasting and spread
out to lead to Cs or Ci layers do they cease to be contrails for the
purpose of cloud classification and reporting? For example, on a day
with no naturally formed cirriform clouds but with contrails that
develop into a 3 okta Cs/Ci cloud cover should this be recorded as 3Ci
or 3Cs along with a RMK that they evolved from contrails, or is it the
case of once a contrail, always a contrail and a RMK made along the
lines of "Extensive contrails, spreading to form Cs/Ci" with no
comment made upon the extent of cloud cover? I observe many contrails
being situated under several flight paths. I would be very grateful
for some guidance on how one should classify and report man made
cirriform.

Many thanks,

Ian,

Raunds, East Northants. 63m. Grid Ref SP9972
---------------------------------------------------------------------

On 20 Sep, 19:22, "Bernard Burton"
wrote:
Ian, I do not know if there is any official rulings about this subject, but
personally I report COTRA as a remark if any of the observed cirrus is of
identifiable aircraft origin. There are not many occasions in this area,
there being many overflying jets, that the is doubt or ambiguity about
whether to report COTRA. Contrail cirrus counts towards cloud amount in an
observation, and contributes towards an assessment of the cloud type for
coding purposes.

--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:www.woksat.info/wwp.html
orwww.btinternet.com/~wokingham.weather/wwp.html"Ian" wrote in message

ps.com...



Hi all,

I wonder if anybody could offer some advice on contrail observation?
When conditions are right and contrails are long lasting and spread
out to lead to Cs or Ci layers do they cease to be contrails for the
purpose of cloud classification and reporting? For example, on a day
with no naturally formed cirriform clouds but with contrails that
develop into a 3 okta Cs/Ci cloud cover should this be recorded as 3Ci
or 3Cs along with a RMK that they evolved from contrails, or is it the
case of once a contrail, always a contrail and a RMK made along the
lines of "Extensive contrails, spreading to form Cs/Ci" with no
comment made upon the extent of cloud cover? I observe many contrails
being situated under several flight paths. I would be very grateful
for some guidance on how one should classify and report man made
cirriform.

Many thanks,

Ian,

Raunds, East Northants. 63m. Grid Ref SP9972
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- Show quoted text -


Bernard & Stephen,

Many thanks for your advice and guidance, it is much appreciated.

Ian.

Raunds, East Northants. 63m. Grid Ref SP9972
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