Estimating

[ASpilot2be]

Why does a controller announce "estimating" during some calls?

For example today on the ATIS it said "the altimeter is estimated to be at 30.28", and then before takeoff the tower announced "cleared for takeoff, the wind is estimated to be calm".

I suspect the weather machine was broken, but what is the reason for "estimating" the wind to be calm when they can look at the windsock? It seemed alittle weird.

 

[TFaudree_ERAU]

when they can look at the windsock?

And by doing that they're deriving a wind direction and speed how?

I guess it all comes down to liability. If there is no machine to tell them exactly what the weather conditions are, it's all estimating

 

[tykrtr]

And by doing that they're deriving a wind direction and speed how?

BEAUFORT SCALE Baby!
<1 Wind Calm: smoke rises vertically
1-3 Direction of wind shown by smoke drift but not wind vanes
4-6 Wind felt on face (don't ask how to do that from the tower) leaves rustle, vanes moved
7-10 Flags extend...

I guess it all comes down to liability. If there is no machine to tell them exactly what the weather conditions are, it's all estimating

Exactly correct. Machine broken, estimate something based on observations. Another example, if you aren't sure if your gear is down and do a flyby so the tower can observe, they will say it "appears" down. Once upon a time, I'm sure the FAA bought an airplane because someone said their gear WAS down and it wasn't.

 

[TXTBOOK]

I thought wind 3 or less was calm?

 

[FM_Weasel]

Less than 3. That list is more of a visual reference to estimate the wind. Doesn't really override how the wind is reported to pilots by ATC.

 

[aorta]

Using a windsock
-less than 3 knot winds Calm
-wind has air moving though sock horizontally without being fully extended
3 to 14 knot winds maybe gusting don't be a wuss
-windsock fully extended 15 to 50 knot winds maybe gusting
-windsock missing find alt. airport, it's crazy windy or as Ollie Williams would say "IT'S RAININ' SIDEWAYS!"

:dunno:

 

[Alpha Lima]

If they are saying winds estimated that means they dont have live winds. They are just reading the winds off of the last METAR. So if its METAR KBOI 092153Z 33014G23KT and their equipment that feeds them live winds/altimeters is down they would issue it as "wind estimated 330 at 14 gust 23".

 

[tykrtr]

If they are saying winds estimated that means they dont have live winds. They are just reading the winds off of the last METAR. So if its METAR KBOI 092153Z 33014G23KT and their equipment that feeds them live winds/altimeters is down they would issue it as "wind estimated 330 at 14 gust 23".

Possibly, but not necessarily. The previous METAR could include estimated winds as well. We might also use a source that isn't exactly "certified" to "estimate" winds (calibrated eyeball?).

You're right, though, it means we don't have a "certified" wind display and we're literally making it up! Technically The FMH-1 http://www.ofcm.gov/fmh-1/fmh1.htm describes how to report winds but it is actually a summary. There are more explicit instructions for weather observers (NWS gets pretty anal about their weather)...