JIC U do not use this...
www.bom.gov.au/marine/wind.shtmlclick in to zone of interest.
I use this as a good predictor there is a local focus zone around capital cities for 48 hrs in advance..
The main variable will be sea-breeze - hopefully someone Sydney way can give you parameters...
Locally in summer months (Sunny Coast) The SB tends to kick in with 26C+ on the forecast - and will swing the wind towards a NE by 20-40 degrees if it is naturally blowing from NW thru' to S and can add up to 12 knots.
It can help to pickup on ISOBAR (pressure) charts (In Southern hemisphere) the high pressure has anti-clockwise wind flow and the low pressure clockwise - the basis for forecasts. The closer the pressure lines the stronger the wind.
U will always get caught out by the wind but experience helps

The best way I have found to insulate myself from low winds stuffing the day is a big board - my weapon of choice - SECTOR 60

Cheers
AP