The escarpment is high, like a huge wall penning the Illawarra against the sea. OK, not that high, but high enough. The average altitude of Thirroul is apparently around 20 metres, while the escarpment can be up around 800 metres, or about 2600 feet; a reasonably decent climb for a light aircraft. When you drive up the winding road from the coast to the escarpment, and your car is loaded... the engine does feel it.

And this altitude difference often means that what would be clouds over the coast become mist and fog banks when they hit the escarpment.

Just as we see here.