Yes, a Category 5 - started out small swelled to a Cat 5, dropped to a 3, then back up to a 5 over the Gulf of Carpentaria Sea, as strong as Cyclone Tracy 30 years ago. Darwin was rebuilt to withstand much greater destructive force than originally due to Tracy, so hopefully things should not be as nasty this time if it heads close to Darwin. Winds over 250Km/hr are rather devastating.