I was taught that for fog to be reported, visibility had to be less than
1000 metres. But Camborne has been reporting fog all day although
visibility has always been around 5 km.
http://www.metoffice.gov.uk/weather/...t_weather.html
shows what I'm talking about.
Maybe my knowledge needs updating.
--
MCC

"MCC" wrote in message ...
I was taught that for fog to be reported, visibility had to be less
than 1000 metres. But Camborne has been reporting fog all day
although visibility has always been around 5 km.
http://www.metoffice.gov.uk/weather/...t_weather.html
shows what I'm talking about.
Maybe my knowledge needs updating.


The SYNOP is reporting (this is the 15Z example below) ... in the
weather group ... "74011", where the '40' is decoded as stated below.

03808 41250 23506 10153 20133 30169 40276 57004 74011 81671 91450
333 55310 22977 81703=


" 40: Fog or ice fog at a distance at the time of observation, but not
at the
station during the preceding hour, the fog or ice fog extending to a
level above that of the observer. "


I believe that it is still permissible to report such with the
*general* visibility [ lowest vis still with the SYNOP, rather than
the 'prevailing' vis as with a METAR ] above 1 km.

I assume, from the VIS imagery, that they can see (from a nominal
station elevation of 88 m), a bank of fog that has managed to
penetrate inland from the western shore.
The algorithms that interpret the SYNOP data obviously aren't clever
enough to pick out the fact that there is often (as on this ob) a full
hour of direct solar radiation (55310) with little significant cloud
present.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

On 9 Jun, 16:52, MCC wrote:
I was taught that for fog to be reported, visibility had to be less than
1000 metres. But Camborne has been reporting fog all day although
visibility has always been around 5 km.http://www.metoffice.gov.uk/weather/...t_weather.html
shows what I'm talking about.
Maybe my knowledge needs updating.
--
MCC

You're perfectly correct in your recollection. But checking the
Camborne synops for 09, 12, 15z shows ww = 40, which is distant (or
adjacent) fog. So the observer can see a bank of fog nearby,
presumably within 5 km as that's the reported visibility, and is quite
correctly reporting it in the present weather, although the visibility
at the observing site itself is 1000 metres (and the RH is 95% as
well). I guess it's probably a fog bank over the nearby coast.

Mystery solved ... and not even by a paid-up member of the SouthWest
usw club either ;-)

--
Stephen Burt
Stratfield Mortimer, Berkshire

Martin Rowley wrote:
"MCC" wrote in message ...
I was taught that for fog to be reported, visibility had to be less
than 1000 metres. But Camborne has been reporting fog all day
although visibility has always been around 5 km.
http://www.metoffice.gov.uk/weather/...t_weather.html
shows what I'm talking about.
Maybe my knowledge needs updating.


The SYNOP is reporting (this is the 15Z example below) ... in the
weather group ... "74011", where the '40' is decoded as stated below.

03808 41250 23506 10153 20133 30169 40276 57004 74011 81671 91450
333 55310 22977 81703=


" 40: Fog or ice fog at a distance at the time of observation, but not
at the
station during the preceding hour, the fog or ice fog extending to a
level above that of the observer. "


I believe that it is still permissible to report such with the
*general* visibility [ lowest vis still with the SYNOP, rather than
the 'prevailing' vis as with a METAR ] above 1 km.

I assume, from the VIS imagery, that they can see (from a nominal
station elevation of 88 m), a bank of fog that has managed to
penetrate inland from the western shore.
The algorithms that interpret the SYNOP data obviously aren't clever
enough to pick out the fact that there is often (as on this ob) a full
hour of direct solar radiation (55310) with little significant cloud
present.

Martin.


Thank you. So rather than just "fog" it would have been more helpful to
the likes of me if "fog in the vicinity" could be reported :-)
--
MCC

wrote:
On 9 Jun, 16:52, MCC wrote:
I was taught that for fog to be reported, visibility had to be less than
1000 metres. But Camborne has been reporting fog all day although
visibility has always been around 5 km.http://www.metoffice.gov.uk/weather/...t_weather.html
shows what I'm talking about.
Maybe my knowledge needs updating.
--
MCC

You're perfectly correct in your recollection. But checking the
Camborne synops for 09, 12, 15z shows ww = 40, which is distant (or
adjacent) fog. So the observer can see a bank of fog nearby,
presumably within 5 km as that's the reported visibility, and is quite
correctly reporting it in the present weather, although the visibility
at the observing site itself is 1000 metres (and the RH is 95% as
well). I guess it's probably a fog bank over the nearby coast.

Mystery solved ... and not even by a paid-up member of the SouthWest
usw club either ;-)

Thank you. As I said in my reply to Martin, "fog in the vicinity" would
have made more sense to me, rather than just "fog".
I could get the raw synops data but I don't have the knowledge to decode
them.
--
MCC

"MCC" wrote in message
...
wrote:
On 9 Jun, 16:52, MCC wrote:
I was taught that for fog to be reported, visibility had to be
less than
1000 metres. But Camborne has been reporting fog all day although
visibility has always been around 5
km.http://www.metoffice.gov.uk/weather/...t_weather.html
shows what I'm talking about.

You're perfectly correct in your recollection. But checking the
Camborne synops for 09, 12, 15z shows ww = 40, which is distant (or
adjacent) fog. So the observer can see a bank of fog nearby,
presumably within 5 km as that's the reported visibility, and is
quite
correctly reporting it in the present weather, although the
visibility
at the observing site itself is 1000 metres (and the RH is 95%
as
well). I guess it's probably a fog bank over the nearby coast.



.... it is something that needs sorting out actually as the decoded
weather gives a totally false impression of conditions at Camborne
today. I'll send a copy of this thread to the Customer Centre and see
what response I get.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

"Martin Rowley" schreef in bericht
...

: "MCC" wrote in message

: ... Camborne has been reporting fog all day although
: visibility has always been around 5
:
km.http://www.metoffice.gov.uk/weather/...t_weather.html

: You're perfectly correct in your recollection. But checking the
: Camborne synops for 09, 12, 15z shows ww = 40, which is distant (or
: adjacent) fog. So the observer can see a bank of fog nearby,
: presumably within 5 km as that's the reported visibility, and is
: quite
: correctly reporting it in the present weather, although the
: visibility
: at the observing site itself is 1000 metres (and the RH is 95%
: as
: well). I guess it's probably a fog bank over the nearby coast.

: ... it is something that needs sorting out actually as the decoded
: weather gives a totally false impression of conditions at Camborne
: today. I'll send a copy of this thread to the Customer Centre and see
: what response I get.

Have there not been questions on here before about unduly low temperatures
reported from Camborne ? For example today - max. temps Cardinham 22.7°C,
Culdrose 21.9°C, St Mawgan 18.8°C but Camborne only 15.6°C. Is that
plausible ?

Colin Youngs
Brussels

On Mon, 9 Jun 2008 19:41:58 +0100, Martin Rowley wrote:

"MCC" wrote in message
...
wrote:
On 9 Jun, 16:52, MCC wrote:
I was taught that for fog to be reported, visibility had to be
less than
1000 metres. But Camborne has been reporting fog all day although
visibility has always been around 5
km.http://www.metoffice.gov.uk/weather/...t_weather.html
shows what I'm talking about.

You're perfectly correct in your recollection. But checking the
Camborne synops for 09, 12, 15z shows ww = 40, which is distant (or
adjacent) fog. So the observer can see a bank of fog nearby,
presumably within 5 km as that's the reported visibility, and is
quite
correctly reporting it in the present weather, although the
visibility
at the observing site itself is 1000 metres (and the RH is 95%
as
well). I guess it's probably a fog bank over the nearby coast.



... it is something that needs sorting out actually as the decoded
weather gives a totally false impression of conditions at Camborne
today. I'll send a copy of this thread to the Customer Centre and see
what response I get.

Martin.

I'd be interested to read any reply you receive.
Thanks.
--
MCC

"MCC" wrote...
snip

I'd be interested to read any reply you receive.
Thanks.
--
MCC


.... will do; have had the standard acknowledgment.

Martin.


--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023

On 9 Jun, 21:50, "Colin Youngs" wrote:
"Martin Rowley" schreef in ...

: "MCC" wrote in message

: ... Camborne has been reporting fog all day although
: visibility has always been around 5
:
km.http://www.metoffice.gov.uk/weather/...t_weather.html

: You're perfectly correct in your recollection. But checking the
: Camborne synops for 09, 12, 15z shows ww = 40, which is distant (or
: adjacent) fog. So the observer can see a bank of fog nearby,
: presumably within 5 km as that's the reported visibility, and is
: quite
: correctly reporting it in the present weather, although the
: visibility
: at the observing site itself is 1000 metres (and the RH is 95%
: as
: well). I guess it's probably a fog bank over the nearby coast.

: ... it is something that needs sorting out actually as the decoded
: weather gives a totally false impression of conditions at Camborne
: today. I'll send a copy of this thread to the Customer Centre and see
: what response I get.

Have there not been questions on here before about unduly low temperatures
reported from Camborne ? * For example today - max. temps Cardinham 22.7°C,
Culdrose 21.9°C, *St Mawgan 18.8°C but Camborne only 15.6°C. * Is that
plausible ?

Colin Youngs
Brussels

Yes, I've repeatedly raised the issue, but no reponse, I've given up
recently. It's not just odd days, but the average Max over a month is
often 2C lower than the higher & more exposed north coast location at
St. Mawgan. The mins seem OK, but the max often seems impossible. I've
been long convinced that Camborne Max Temps are low. There have been
many occasions when Camborne's been clear of the fog, St Mawgan &
Scilly have been in fog, and they have have still be warmer.

Graham
Penzance
maxes

Graham
Penzance