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Certain maritime ports and airports have ranges of operation relation to the wind, usually according to a given threshold value of sustained wind speed. If I have the instantaneous values from anemometer every 50 seconds, how can I determine that the sustained wind speed exceeded the threshold?

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    $\begingroup$ What do you mean by steadily? It seems like all you need is to perform some temporal averaging on the anemometer samples. $\endgroup$ – Isopycnal Oscillation Nov 14 '14 at 21:17
  • $\begingroup$ Sorry, I mean once the windspeed attains a sustained 45 knots, in example $\endgroup$ – Mmeyer Nov 14 '14 at 21:34
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    $\begingroup$ Very little detail is given in this question. Furthermore, airplanes are not kept from landing/taking based on wind speed alone (unless the airport closes due to something like a hurricane). The effect of crosswind, turbulence, and windshear are most important. In aviation, a steady wind speed value is one void of large gusts or variance. So, if you were using your instantaneous values, you would want to take the mode of the numbers over a few minutes (e.g. what wind speed was reported the most?). All in all, though, this sounds like a question better suited for aviation stack exchange. $\endgroup$ – farrenthorpe Nov 14 '14 at 21:42
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You are essentially asking how to determine what the sustained wind speed is, and as pointed out in a comment, this is merely temporally averaging your 50 s instantaneous wind observations. The specific application you are targeting likely has a standardized definition of a time period over which the averaging should occur. This might be a 3 minute wind, a 5 minute wind or some other value. Once you know this value, you can calculate a rolling average over your time series of instantaneous wind and this rolling average is your "sustained" wind.

If your application is aviation, you'll want to keep the sustained wind and the peak winds, as the difference between sustained and peak gust is important to landing aircraft (we call that difference the "gust factor" and is generally more important than the sustained wind alone).

METAR define wind direction and speed as 2 minute averages and define gusts as a minimum 10 kt deviation over the mean during a 10 minute period. See this page for more information on observing wind for METAR applications.

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