On 08/11/2010 21:28, Jon O'Rourke wrote:


Not guilty m'lord on this occasion !

From a TAF perspective it all depends on the the extent of the change
in terms of degrees and also the speed before and after the change.
However, in this case it a change to 130° to 210° would be valid in the
TAF as it was a swing of 60° or more and the wind was over 10KT before
it veered - but no doubt difficult to predict accurately for such a
short time. If you were writing a TAF based on the what happened it
would quite awkward, either a short BECMG of a SW'ly immediately
followed by another short BECMG back to a SE'ly or alternatively a TEMPO
SW'ly for 1 hour. Either way it's a difficult one to convey well within
the constraints of the TAF rules.

As an aside, have you tried the Openrunway service for Heathrow, Phil ?
I'm sure you'd find that interesting and it also provides hourly
predictions for wind speed and direction amongst other parameters
http://www.metoffice.gov.uk/aviation...rts/openrunway

Jon.

I would go for a TEMPO! It was clearly a fine line. Farnborough were
Westerly for a few hours, and Gatwick never made it even though Shoreham
did! It was certainly a wonky old front!

Phil