Biggin Hill has been showing temps of 3°C all day, whereas here
at Warlingham (4 miles west, same altitude) it has not got above 1.5°C
and is now (1430) down to 1.0°C. Gatwick and Heathrow have both got
2°C. Nothing wrong with my thermometers, unless they're *both* low
(they're not), or exposure. The visibility (2500 m) at Biggin Hill
also looks too low (about 3 miles, 5000 m here) as does their QNH
(1033), 2 mb lower than Gatwick, Heathrow and here. A year or so ago
Biggin Hill temperatures were definitely too low. Well, they've
overcorrected by about 100%. It doesn't give one much confidence in
METAR's and makes you wonder who actually carries out the observations.


Tudor Hughes, Warlingham, Surrey. 556 ft.

"Tudor Hughes" wrote in message
ups.com...
Biggin Hill has been showing temps of 3°C all day, whereas here
at Warlingham (4 miles west, same altitude) it has not got above 1.5°C
and is now (1430) down to 1.0°C. snip The visibility (2500 m) at
Biggin Hill
also looks too low (about 3 miles, 5000 m here) as does their QNH
(1033), 2 mb lower than Gatwick, Heathrow and here. snip
It doesn't give one much confidence in
METAR's and makes you wonder who actually carries out the observations.

.... as you say, these differences are *very* worrying, particularly the
QNH discrepancy. I know we've moved on from the days of a forecaster &
observer working in an office and cross-checking against charts etc.,
but it does demonstrate the benefit of that system. It also implies that
the staff aren't really interested in what they are putting out - again
the QNH error would have been regarded as a cause for a minor 'flap'
with check barometers (in the days of PABAR's) being demanded in a hurry
from Bracknell etc. Obviously there is no system of double-barometer in
operation, or else, the correction tables have been erroneously set up?

Martin.

My readings concur with Tudor and he definitely has a point. Temperature has
been slowly falling from 09.00hrs obs. of 1.8C to 1C at present mid
afternoon and my altitude is both not far off Biggin Hill nor that far away.
I know there is an inversion above us but not at Biggin Hill's altitude.
Ian Currie-Coulsdon,Surrey.

"Tudor Hughes" wrote in message
ups.com...
Biggin Hill has been showing temps of 3°C all day, whereas here
at Warlingham (4 miles west, same altitude) it has not got above 1.5°C
and is now (1430) down to 1.0°C. Gatwick and Heathrow have both got
2°C. Nothing wrong with my thermometers, unless they're *both* low
(they're not), or exposure. The visibility (2500 m) at Biggin Hill
also looks too low (about 3 miles, 5000 m here) as does their QNH
(1033), 2 mb lower than Gatwick, Heathrow and here. A year or so ago
Biggin Hill temperatures were definitely too low. Well, they've
overcorrected by about 100%. It doesn't give one much confidence in
METAR's and makes you wonder who actually carries out the observations.


Tudor Hughes, Warlingham, Surrey. 556 ft.

On 2006-01-23, Martin Rowley wrote:

"Tudor Hughes" wrote in message
ups.com...
Biggin Hill has been showing temps of 3°C all day, whereas here
at Warlingham (4 miles west, same altitude) it has not got above 1.5°C
and is now (1430) down to 1.0°C. snip The visibility (2500 m) at
Biggin Hill
also looks too low (about 3 miles, 5000 m here) as does their QNH
(1033), 2 mb lower than Gatwick, Heathrow and here. snip
It doesn't give one much confidence in
METAR's and makes you wonder who actually carries out the observations.

... as you say, these differences are *very* worrying, particularly the
QNH discrepancy. I know we've moved on from the days of a forecaster &
observer working in an office and cross-checking against charts etc.,
but it does demonstrate the benefit of that system. It also implies that
the staff aren't really interested in what they are putting out - again
the QNH error would have been regarded as a cause for a minor 'flap'
with check barometers (in the days of PABAR's) being demanded in a hurry
from Bracknell etc. Obviously there is no system of double-barometer in
operation, or else, the correction tables have been erroneously set up?

Martin.



So what would be the risk to aviators of the QNH error? Is it
dangerous?

--
Jon
____________________________________________
jondotrogersatntlworlddotcom
============================================

"Jon Rogers" wrote in message
...


So what would be the risk to aviators of the QNH error? Is it
dangerous?


.... not necessarily 'dangerous' in this case, but shows up that there is
a problem with the equipment and / or procedures, which needs sorting
out before it drifts too far. Barometers can drift off calibration and
regular checking is required to make sure that gross errors (which might
become critical) aren't overlooked.

Martin.


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