Thelma formed Coming_to_be in the Arafura Sea north of the Northern Territory while intensifying Cause_change_of_strength rapidly into a Category 5 cyclone , passing Motion_directional very near the Tiwi Islands and posing Causation a severe threat to Darwin , but passed Motion_directional by at a distance of .

Forming Coming_to_be out of a tropical disturbance over the Arafura Sea on 2 April 1999 , the precursor to Gwenda tracked Motion slowly westward and gradually became Becoming more organised .

The first tropical cyclone Catastrophe of the regional season , Sam originated Coming_to_be from a tropical low that formed Coming_to_be in the Arafura Sea on 28 November .