Wind speed can be calculated by calculating the meridional- and zonal- wind components, which are the wind in the west-east and south-north direction.
To calculate meridional- and zonal- from wind direction and wind speed:
If V = Wind Speed,
D = Wind direction,
u = Meridional wind component,
v = zonal wind componant,
u = V * sin D v = V * cos D
To calculate average meridional- and zonal- wind speed:
Average Wind = sqrt (u2+v2)