Winds at EGLL

[Tonic Please]

Hi all.

I have been meaning to post this for a while, and I am finally encouraged to post due to the wind today!

I have had a scanner for years, and always tune in when the weather is bad to hear some action - and of course, when on Heathrow tower for landings, I hear the wind.

I live 10 miles directly south of LHR. The house faces east to west. For example, right now, the tress infront of the house are being lashed around, it's strong, it's going straight up north. My "annoyance" is this: Whenever the wind is so strong here I can hardly ride my bike, the wind at heathrow is "xxx @ 12 knots". I say to myself "that's impossible". And whenever the wind is not much here, I hear at LHR "Wind xxx @ 22 knots" (for example) HOW?

I just find it impossible that 10 miles south, is a semi-open area, the trees can be bending double yet the wind is nothing at Heathrow just 10 miles north.

Would someone care to explain how this is so? Right now, winds are 230/15 (sometimes G25, which as far as I'm concerned, should be the lowest figure!). Second, how is wind measured at heathrow? From the ground (which is surely unreliable?) or from 50 feet up? (more reliable and useful?)

Any responses welcome.

Regards

[rsuggitt]

Because the weather varies over space and time.

[Spitoon]

ICAO Annex 3 will tell you how the wind is measured.

[RYR-738-JOCKEY]

Measured at threshold for runway in use, 10 meters above ground. But I do understand why you ask. Sometimes it seems strange to us as well. I don't have any experience with Heathrow in particular but for instance Prestwick always under-report their wind with approx 10 knots (compared to the computer onboard at touchdown).

[A Very Civil Pilot]

The reported wind is a 2 min average. If the trees are lashing around at your house, you'll only tend to notice the strong moments, and not so much the quieter moments. Average it out and it may not bee too much different.

[Tonic Please]

Thank you for the responses. The average wind does puzzle me a little more, to be honest, since they give every next plane that lands, a different wind to the one before.

Either way, thanks chaps

[Tight Slot]

If its a strong wind with gusts coming into play, towers will often give out a "Instant wind check" as the aircraft gets short final. Of marginal use by then but makes the sweat trickle down your back a tad faster... (or widen the grin if PNF!)

Regards

[Spitoon]

The average wind does puzzle me a little more, to be honest, since they give every next plane that lands, a different wind to the one before.

The average is a two minute rolling value. So, let's say that aircraft are landing one minute apart, each reported wind is the average over the previous two minutes and will probably be different from that preceding it. Just to make things more interesting, the 'instant' wind that Tight Slot refers to is also actually an average - for most systems I think it's a 5 second rolling average.

The wind reported by ATC has always been averaged. In the old days by an element of hysteresis in the display system and often by the controller making some professional judgement, now we just try to do it more systematically and consistently with electronics.