Estimation of extreme wind speeds in Sweden

Wind speeds in extra tropical latitudes are known to be approximately Weibull distributed. Hence a Weibull distribution fitted to all available data is often used to predict sizes of future extreme winds. The most extreme values then, however, have little influence on the estimated parent Weibull distribution, and the accuracy of the extreme value predictions obtained in this manner may be questioned. In the present paper such a " Weibull method" is compared to a method based on statistical extreme value theory, "the Annual Maxima method". The comparison is based on 30 years of 10 minute wind speed averages measured hourly at 12 meteorological stations located at airports in Sweden. Results include that the Weibull method gives incorrect estimates of the tails of the distributions of wind speeds and of the distribution of yearly maximum wind speeds, that it doesn't provide any confidence bounds for the estimates, and that serial dependence of individual measurements has to be taken into account. The Annual Maxima method avoids these problems. A further, "technical" results is that rounding to entire meters per second decreases the accuracy of estimates, and that if such rounding is done, it should be taken into account in the estimation procedure