Here is a great site that compares the size of this mega-cyclone* with other parts of the world.
Of course a storm of this magnitude is unlikely to develop outside tropical regions, but it just shows you what the Aussies are referring to when they talk about 'cyclone season'. Although they're not usually whoppers like Cyclone Yasi.
Here is it superimposed on Europe...
..and over Asia:
Just the eye, over Katrina country:
*Artificially colour-coded by rainfall density.