Forecast wind this Sat morning is showing 20knots for Perth, but all live graphs are showing 5 knots. (Except Rottnest) What's up with that? Similar thing happened last weekend and I had to cancel my winsurfing plans.
Thanks for any replies - hope I'm not asking something obvious.

It's called - "Gettin' Skunked"

I usually regard the foreast wind to be what Rottnest will get (pretty sure the windmeters are up on a hill over there too), like you say Rottnest got it.

During summer when we're getting regular seabreezes its a much more reliabe forecast, once it starts to get a bit funky though I take it all with a pinch of salt.

A Souwesterly in the morning aint a seabreeze....

^^^^ +1

and the forecast is not for the beach, it is for up to 20km (?) out in the ocean
it seems in the last few years it is designed to talk about absolute maximum wind that the absolute minimum intelligence level boatie might encounter. A warning, rather than a forecast...?

Ok, that lines up with what I'm seeing. Does that mean that the forecast is of no use for river windsurfing? There should really be 2 forecasts then, as everyone not on a boat out at sea will not care much about Rottnest/20km out wind levels.

Meteye

Perth Local Waters Forecast: Two Rocks to Dawesville, inshore from Rottnest Island

My personal Fave for Perth metro
www.bom.gov.au/marine/wind.shtml?unit=p0&location=wa-per&tz=AWST

Thanks For that link Elmo. That BOM wind map forecast is much better

I think it is also this time of the year that makes it notoriously inaccurate, particularly these last 2-3 weeks the forecasts in the SB area have been very optimistic with a few days predicted to be around 25-30 knots, but turning out to be only 15-20.
...I guess we should start aiming and the winter cold fronts.

Anyway to find the location and height of the wind sensors? The www.windalert.com:443/map site shows a bit of information for some sites.

Open

www.bom.gov.au/wa/observations/perth.shtml

Click on the location in the table and it will open up another page with all readings for that particular location

Just above the first table is "Station details"

ie for Mandurakastan

Station Details ID: 009977 Name: MANDURAH Lat: -32.52 Lon: 115.71 Height: 3.0 m