In local routine and special reports and in METAR and SPECI, the surface wind direction and speed shall be reported in steps of 10 degrees true and 1 kilometre per hour (or 1 knot), respectively. Any observed value that does not fit the reporting scale in use shall be rounded to the nearest step in the scale. 4.1.5.2 In local routine and special reports and in METAR and SPECI: a) the units of measurement used for the wind speed shall be indicated; b) variations from the mean wind direction during the past 10 minutes shall be reported as follows, if the total variation is 60° or more: 1) when the total variation is 60° or more and less than 180° and the wind speed is 6 km/h (3 kt) or more, such directional variations shall be reported as the two extreme directions between which the surface wind has varied; 2) when the total variation is 60° or more and less than 180° and the wind speed is less than 6 km/h (3 kt), the wind direction shall be reported as variable with no mean wind direction; or 3) when the total variation is 180° or more, the wind direction shall be reported as variable with no mean wind direction; c) variations from the mean wind speed (gusts) during the past 10 minutes shall be reported when the maximum wind speed exceeds the mean speed by 20 km/h (10 kt) or more; d) when a wind speed of less than 2 km/h (1 kt) is reported, it shall be indicated as calm; e) when a wind speed of 200 km/h (100 kt) or more is reported, it shall be indicated to be more than 199 km/h (99 kt); and f) when the 10-minute period includes a marked discontinuity in the wind direction and/or speed, only variations from the mean wind direction and mean wind speed occurring since the discontinuity shall be reported.
Posted on: Tue, 25 Jun 2013 08:50:32 +0000
Trending Topics
Recently Viewed Topics
© 2015