## 6 Reporting Practices  
The World Meteorological Organization (WMO) provides guidelines for meteorological observations and their international exchange, which has been based on alphanumeric codes that have later been replaced mostly by binary formats. WMO recommends measuring wind gust speed as a 3-s average of wind speed during a 10-min sampling interval [29]. However, there exists differences in both measurement and reporting practices, and these may vary at the regional and national level.  
The traditional WMO alphanumeric codes for surface observations are called SYNOP (surface synoptic observations; fixed land stations), SYNOP MOBIL (mobile land stations) and SHIP (ship synoptic observations; sea stations) [105]. In general, these codes do not include wind gusts, although deviations from the standards exist at the national level (for example, in Argentina, the maximum hourly gust speed is reported if the observed gust is equal to or higher than 30 knots (\(\approx\)15 ms\({}^{-1}\)) [106]). The codes called METAR (METeorological Aerodrome Report) and SPECI (aviation SPECIal weather report) used for aerodrome routine reports include gusts, but they are reported only if the wind gust speed, defined as a 3-s average, exceeds the 10-min mean wind speed by 5 ms\({}^{-1}\) (10 knots) or more [105].  
The binary formats regulated by WMO are called BUFR (Binary Universal Form for the Representation of meteorological data) and GRIB (GRIdded Binary or General Regularly-distributed Information in Binary form) [107]. The latter comprises regularly-distributed information such as gridded data from NWP systems. BUFR, on the other hand, is a binary universal form for the representation of meteorological data and is used for the exchange of surface observations, but also of many other types of meteorological measurements and forecast information. In BUFR format, wind gusts can be reported both from land and sea stations (SYNOP and SHIP stations), as well as from aerodrome reports (METAR/SPECI).  
Despite the WMO recommendations for wind gust measurements, the measurement and recording practices may vary regionally and nationally. For example, in the ASOS network in the USA, wind gusts are recorded as the maximum 5-s average of wind speed during the past 10-min period preceding the time of observation. At the same time, the averaging time for the mean wind speed is 2 min instead of 10 min. Moreover, wind gusts are reported only if the highest gust during the past 10 min exceeds the 2-min mean wind speed by at least three knots, given that the mean wind speed is greater than two knots, and the highest gust exceeds the minimum five-second wind speed during past 10 min by 10 knots or more. In other words, the minimum reported wind gust speed is 14 knots. In addition, the peak wind may be reported as the highest 5-s average of wind speed that exceeds 25 knots since the last hourly (METAR) observation [108]. Although at ASOS stations, the wind gust duration has traditionally been 5 s instead of 3 s, at some locations, the 3-s gust duration was adopted later [42].  
Different measurement and recording practices make the intercomparison of observed wind gusts challenging. Therefore, it is crucial that the averaging periods are well documented and available for data users. For example, if the wind gusts are reported only when a certain threshold value is exceeded, the resulting wind gust statistics are not representative of the actual wind gust climate observed at the measurement site. However, if the wind gust speed is recorded only during the last 10-min period preceding the observation time at each hour, the resulting gusts will always be equal to or weaker than the true maximum wind gust during the preceding hour [42]. This is of particular concern in design load calculations, where the aim is to estimate the probability of occurrence of extreme wind gusts with return periods typically from 10-50 years or more.