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In a METAR report gusts of wind are shown with a G after the wind speed. When will gusts be reported? I have seen reports that show:

  • 12017G20
  • 12010G20
  • 12003G20
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The definition of "Wind Gust" for METAR reports can be found in the Federal Meteorological Handbook No. 1, chapter 5:

5.4.4 Wind Gust. The wind speed data for the most recent 10 minutes shall be examined to evaluate the occurrence of gusts. Gusts are indicated by rapid fluctuations in wind speed with a variation of 10 knots or more between peaks and lulls. The speed of a gust shall be the maximum instantaneous wind speed.

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    $\begingroup$ The statement here "variation of 10 knots or more" seems at odds with examples like the "12017G20" in the OP. How come it isn't reported as 10G20 in that case? $\endgroup$
    – Ralph J
    May 2 '16 at 13:44
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    $\begingroup$ Because gusts go both ways: faster and slower winds. So 17G20 means 17 steady and gusting as low as 10 or as high as 20. $\endgroup$
    – rbp
    May 2 '16 at 15:50
  • $\begingroup$ WMO standard defines a gust as the maximum wind speed exceeding the "mean speed" by 5 m/s (10 knots) during the 10-minute interval. $\endgroup$ Oct 14 '20 at 17:54

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