Hi Dianna
BOM are competing with all these other services.
I don;t know if you've seen this new BOM product Forecast explorer. It predicts marine weather in 6km square blocks. YOU can see that there is great variability along the coast. That is one of the reasons they have so much trouble predicting the weather.
http://www.bom.gov.au/forecasts/graphic ... x-week.php
Put your cursor over Sydney and click for a finer detail.
You did exactly the right thing. With all the information to hand, you stuck your head out and made a decision to not go. Full marks.