What is annual mean wind speed (AMWS)

Annual mean wind speed - AMWS - is used as the basis for assessing the suitability of a site. It represents the average wind speed experienced at a site over one year.
It is important to note however that AMWS figures do not provide the whole picture - while sites may share the same AMWS figure, some may have steady winds, some much more variation (calm then storm). As the output of a turbine is proportional to the wind speed cubed, sites with periods of strong winds may be superior to those of more steady lower winds (actual performance depends on wind speed distribution and turbine characteristics).