Jon,

Awkward low cloud needing two TAF amendments shortly after issue...

2 oktas here in Guildford

TAF AMD EGLL 180553Z 1806/1912 27010KT 9999 BKN005
BECMG 1806/1808 SCT035
PROB40 TEMPO 1814/1818 28015G25KT
TEMPO 1910/1912 29016G27KT=

FT 18/06/2009 04:59- TAF EGLL 180459Z 1806/1912 27010KT 9999 SCT035
PROB40 TEMPO 1814/1818 28015G25KT
TEMPO 1910/1912 29016G27KT=

FT 18/06/2009 04:23- TAF AMD EGLL 180423Z 1804/1906 27010KT 9999 FEW006
SCT035
TEMPO 1804/1806 8000 BKN006
TEMPO 1814/1818 27015G25KT=

FT 17/06/2009 23:00- TAF AMD EGLL 180423Z 1804/1906 27010KT 9999 FEW006
SCT035
TEMPO 1804/1806 8000 BKN006
TEMPO 1814/1818 27015G25KT=

FT 17/06/2009 22:57- TAF EGLL 172257Z 1800/1906 27010KT 9999 SCT035
TEMPO 1814/1818 27015G25KT=

Phil

--
www.layton.me.uk/meteo.htm

The metar history show that the 500 feet forecast was correct.

But tell me Phil. Is 500 feet stratus cloudbase significant from the
controller’s point of view? (as opposed to an earlier TAF giving
nothing below 3,500). Even in my flying days (goodness, I retired
almost 11 years ago!) 500 feet wouldn’t have made the slightest
difference to us so it can’t do so in 2009. But does the landing/take
off flow rate have to be changed in such conditions of low cloud even
with good visibility beneath?

Jack

wrote in message
...
The metar history show that the 500 feet forecast was correct.

But tell me Phil. Is 500 feet stratus cloudbase significant from the
controller’s point of view? (as opposed to an earlier TAF giving
nothing below 3,500). Even in my flying days (goodness, I retired
almost 11 years ago!) 500 feet wouldn’t have made the slightest
difference to us so it can’t do so in 2009. But does the landing/take
off flow rate have to be changed in such conditions of low cloud even
with good visibility beneath?

Jack - no 500ft is not an issue for us. 400ft we would be looking at
safeguarding, and 300ft we may be 'Tower In Cloud' or ICAO Visibility 2
condition to give it its proper title. Operationally, we are told that any
cloud is not a problem for the flight crews - just the RVRs. All that
matters is whether the approach is flown manually or autoland. Incidentally,
we hope to change LVP introduction from BKN002 to BKN001 soon. We have
agreement in principle from the regulator to apply LVPs when the cloud
ceiling is below 200ft as opposed to 200ft or below - which in practice
means anywhere from 100 to 199ft.

Phil

On Thu, 18 Jun 2009 20:33:50 +0100, Phil Layton wrote:

snip
Incidentally, we hope to change LVP introduction from BKN002 to BKN001
soon. We have agreement in principle from the regulator to apply LVPs
when the cloud ceiling is below 200ft as opposed to 200ft or below -
which in practice means anywhere from 100 to 199ft.

For we clueless ones... that seems to be a change of precisely one foot,
and thus it seems strange that it's important - but I'm assuming there's
more to it than that?

--
Bewdley, Worcs. ~90m asl.

"David Buttery" wrote in message
...
On Thu, 18 Jun 2009 20:33:50 +0100, Phil Layton wrote:

snip
Incidentally, we hope to change LVP introduction from BKN002 to BKN001
soon. We have agreement in principle from the regulator to apply LVPs
when the cloud ceiling is below 200ft as opposed to 200ft or below -
which in practice means anywhere from 100 to 199ft.

For we clueless ones... that seems to be a change of precisely one foot,
and thus it seems strange that it's important - but I'm assuming there's
more to it than that?


Sorry Dave. The ceiliometer records down to the nearest 100ft, so when we
currently have 299ft (being a bit extreme to make a point) cloud ceiling it
is recorded as 200ft OVC002. When it is 180 ft it is recorded as 100ft
OVC001. So the change is from 1 foot to 100feet.

Phil

On Thu, 18 Jun 2009 21:50:56 +0100, Phil Layton wrote:

Sorry Dave. The ceiliometer records down to the nearest 100ft, so when
we currently have 299ft (being a bit extreme to make a point) cloud
ceiling it is recorded as 200ft OVC002. When it is 180 ft it is recorded
as 100ft OVC001. So the change is from 1 foot to 100feet.

Phil

Ah, that makes sense. Thanks for the succinct explanation.

--
Bewdley, Worcs. ~90m asl.