thanks for that link David.
so Height above ground seems to be for WU to add a correction factor to your WIND data as most people dont have it at the ideal height, which may explain why my wind speed readings on wu seem to be higher than shown on my console.
I am personally more interested in the wind speed at low level for when I go out on my bike, but I suppose the readings at the ideal height are for weather prediction, but I imagine most people are using wu to see the conditions that apply to them personally, rather than making a contribution to forecast data.