PPRuNe Forums - View Single Post - Met Office Weather Forecast? Hmmmmmmm....
Old 22nd Jun 2008, 16:59
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bookworm
 
Join Date: Aug 2000
Location: UK
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My CFI made the point about yesterday's TAF showing no rain at all; what if someone decided to take a trip to Edinburgh based on that TAF and got caught out by the nasty weather that appeared instead? Unfortunately I don't have the TAF at hand but it showed few/scattered clouds at about 3000 feet or thereabouts and light winds - no mention of rain. Then the TAF was changed to show the rain... fair enough but why was it taken off the TAF in the first place, bearing in mind that the previous TAF had rain to start with?
OK here's the full sequence of short TAFs yesterday:

TAF EGPH 210544Z 210716 09006KT 9999 FEW040 TEMPO 1516 8000 -RA BKN012=
TAF EGPH 210906Z 211019 VRB03KT 9999 FEW040 BECMG 1114 07011KT=
TAF EGPH 211204Z 211322 07009KT 9999 FEW040 BECMG 1114 07011KT BECMG 1921 8000 -RA BKN014 TEMPO 2122 4000 RA BKN007=
TAF EGPH 211448Z 211601 07012KT 9999 -RA SCT018 BKN035 TEMPO 1921 8000 RA BKN014 BECMG 1921 8000 BKN012 TEMPO 2101 4000 RA BKN007 PROB30 TEMPO 2301 3000 RADZ +RA BKN004=
TAF EGPH 211750Z 211904 11012KT 9999 -RA SCT018 BKN035 TEMPO 1921 8000 RA BKN014 BECMG 1921 8000 BKN012 TEMPO 2104 4000 RA BKN007 PROB30 TEMPO 2304 3000 RADZ +RA=

Here are the METARs from about mid-day (the morning was a boringly accurate prediction):

METAR EGPH 211250Z 06011KT 9999 FEW025 13/09 Q1015=
METAR EGPH 211320Z 06011KT 9999 FEW025 SCT045 13/09 Q1015=
METAR EGPH 211350Z 06012KT 9999 -DZ FEW025 SCT040 12/09 Q1014=
METAR EGPH 211420Z 05010KT 9999 FEW025 SCT040 13/10 Q1014=
METAR EGPH 211450Z 13012KT 9999 FEW025 SCT040 15/08 Q1014=
METAR EGPH 211520Z 15013KT 9999 FEW025 SCT040 15/06 Q1013=
METAR EGPH 211550Z 13012KT 9999 FEW025 14/06 Q1013=
METAR EGPH 211620Z 13012G23KT 9999 -DZ FEW030 13/07 Q1013=
METAR EGPH 211650Z 13011KT 9999 -DZ FEW025 BKN045 12/07 Q1013=
METAR EGPH 211720Z 11009KT 9999 -RA FEW025 BKN045 11/08 Q1012=
METAR EGPH 211750Z 10009KT 9999 -RA OVC035 11/08 Q1011=
METAR EGPH 211820Z 09011KT 9999 -RA FEW018 SCT026 BKN035 10/08 Q1011=
METAR EGPH 211850Z 09011KT 9999 -RA FEW016 BKN030 09/07 Q1010=
METAR EGPH 211920Z 08011KT 9999 -RA FEW009 SCT020 BKN026 09/07 Q1010=
METAR EGPH 211950Z 08011KT 9999 -RA FEW009 SCT012 BKN018 09/08 Q1009=
METAR EGPH 212050Z 08014KT 9999 -RA FEW006 SCT009 OVC014 09/08 Q1008=
METAR EGPH 212020Z 07013KT 6000 -RA FEW008 SCT010 BKN016 09/08 Q1009=
METAR EGPH 212150Z 07014KT 8000 RA FEW006 SCT007 BKN009 09/08 Q1007=
METAR EGPH 212120Z 07013KT 9000 -RA FEW005 SCT009 BKN012 09/08 Q1007=
METAR EGPH 212220Z 07015KT 9999 -RA FEW005 BKN007 10/09 Q1006 RERA=
METAR EGPH 212250Z 08014KT 9999 RA SCT005 BKN007 10/09 Q1005=
METAR EGPH 212320Z 07014KT 7000 RA FEW005 SCT006 10/09 Q1005=
METAR EGPH 212350Z 07012KT 9000 RA FEW003 SCT004 BKN007 10/10 Q1004=

You complaint seems to be that the 1019 TAF didn't predict rain. It took until 1204Z for the Met Office to issue a TAF with a deterioration from 1900, and only at 1448 did they actually predict light rain from 1600. The light rain actually started around 1600.

But just take a look at the operationally important variables. The ceiling didn't fall below 3000 ft until after 1900. The visibility remained at least 10 km until after 1900. In RAF terminology, Edinburgh was actually Blue (the "best" colour state) for the entire period of the 1019 TAF.

Unless your aircraft is made of icing sugar that dissolves in light rain, would you really have been "caught out"?
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