Great question.
I did a google and just found this which expect would answer the question...............got a headache already..............
journals.ametsoc.org/view/journals/wefo/19/2/1520-0434_2004_019_0181_wfftse_2_0_co_2.xmlBeing far more open Botany Bay winds are normally easier to predict than the harbour but of course there are challenging days. Never trust a westerly wherever you are. Southerly busters are usually easy to predict with the cloud build up - but some occur out of a clear sky........
The land thermals have an impact on light breezes - if the land thermals don't occur as predicted then the typical east coast noreaster can become "blocked". Numerous times the forecast for nw breezes to go ne have not occurred in Botany Bay - the ne has happened offshore but doesn't get into the bay.
The marine forecasts are different to general forecasts.
www.bom.gov.au/marine/wind.shtml