Phoney said..
What is the "seabreeze convection" and why doesnt the northern beaches get the same amount of wind as elsewhere in Sydney?
Think back to your geography lessons from school. The hot air in summer generated in Sydneys western suburbs rises up as the day warms. Since Sydney is a basin, trapped between the coast and the Bue Mountains, that air has to be replaced, so it sucks in cooler air from over the ocean. A convection current is set up. Our seabreeze on the coast is the rest of this cycling of air. The northern beaches because of the escarpment close behind don't have access to this convection.