Keygrip
I was fortunate in that I was a racing dinghy sailor for many years before I learnt to fly. Characteristics of winds at suface level whether at sea or with many varieties of surface obstruction, when on rivers etc., get learnt about the hard way, especially when you have worked so hard during a race to use the gusts, etc to come in first, and the other guy judges it better!
Gusts over open water can be very sudden, and from a significantly different direction than the average. They arise from the consequence of thermals - what goes up must come down. Downdrafts will carry the 2000ft+ wind right down to the surface which is sometimes over twice the average surface speed, and in the northern hemisphere will be veered by as much as 15deg from the surface average. They are generally very local to cumulus clouds.
I understand that the Met Office uses forecasts of the amount of vertical activity and wind speed at the various altitudes to forecast the gust speed.
Much more severe are the downdraughts in the vicinity of thunderstorms, microbursts, one of which caused the fatalities in the DC10 crash landing at Faro.
MikeJ
Last edited by MikeJ; 12th Nov 2006 at 07:38.