Russh - The wind meters in the nothern beaches are reasonably accurate.
when the black pole says its blowing 20 knts from the SW it generally is blowing 20 at Bower road
Adelaide Airport is accurate for waters around West beach but trying to predit what Sealiff is doing from this meter is a little more difiult as you know the SE @ Sealiff have a tendency to kill the SW blowing further up the gulf. When predicting what seacliff is doing you need to take into account what sellecks is doing and what Outer harbour is doing. i.e wind strenght and direction.
the southern meters have a few problems. Norlunga on certain wind directions reads lower than what is on the water beause it gets shadowed by Buildings hence 15Kt NW's is very often 20Kt + on the water
Selecks is another story as the meter sits on top of Sellecks hill. when predicting if the wind is going to blow down out of the hill you need to look at how strong the SW seabreeze is at outer harbour.
If it's 30Kt's from the SE at sellecks and 20-25 Kts from the SW at Outer harbour its likely that on the water at selecks is 10 - 15 kts SE or less
as the seabreazes get less strength on the northern beaches Selleks starts to fire as there is less resistance from any seebreaze trying to canel the SE out
hope this has given you a little insite on predicting what the wind is going to do.
then again I could also just be full of S**T and blowing it out of my arse
you can make your mind up about that