Well, Sydney's in this basin - ringed by mountains to the north, west and south, with the ocean to the east and a large body of water in it - it's a temperate climate here, and the weather comes from the south east, so you quite often get good storms through here. Freaky storms are fairly common - the one in the pictures actually missed most of the city, it passed south.
About a month after we moved to Sydney there was a freaky hail storm that went through and caused millions of dollars of damage to cars and rooves - great fun. I remember driving home from the city about half an hour before the storm hit and a rain drop hit the windscreen right in front of my face - it made the loudest smack on the glass you ever heard, and left a watermark the size of a dinner plate on the windscreen.