After forming over the Arafura Sea , the Tracy moved south and hit the city with Category 4 winds on the Australian cyclone scale . It is possible that it had reached Category 3 on the Saffir-Simpson Hurricane Scale when it made landfall . After forming over the Arafura Sea , the storm moved southwards and affected the city with Category 4 winds on the Australian cyclone intensity scale , while there is evidence to suggest that it had reached Category 3 on the Saffir-Simpson Hurricane Scale when it made landfall .