Sandy was the most intense cyclone in the Northern region and the second most intense cyclone in the Eastern region for the 1984-85 season. In a remarkable coincidence Sandy, on 21 March 1985, was positioned just 70 km away from where cyclone Kathy had been located exactly one year earlier.
Sandy formed from a cyclonic circulation embedded in the monsoon trough over northeast Arnhem Land. This circulation drifted over the tropical waters. After reaching tropical cyclone intensity at about 1200 UTC 20 March, Sandy remained almost stationary for 36 hours intensifying in the process. The cyclone moved into the Eastern region for about 55 hours during 21,22 and 23 March. Although Sandy was classed as a severe tropical cyclone, satellite imagery showed that unlike Kathy, Sandy had a ragged eye and hence was not as intense. When Sandy finally began to move the cyclone tracked south-southwest towards the coast and then west-northwest along the coast. Sandy passed just north of the Sir Edward Pellew Group of islands at about 0000 UTC 24 March where the Centre Island meteorological station recorded a minimum pressure of 973 hPa, a maximum wind speed of 170 km/h and a maximum gust of 220 km/h. Two trawlers, the Hayman and the Sea Fever were beached by their crews after experiencing gusts well over 200 km/h' and swells as measured by their depth sounders of 12m. Storm surges measured by a Bureau survey team were 3 to 3.5 m at Centre Island and coastal surveillance flights reported a pilot whale 1 km inland. Flooding was extensive along the southern gulf coast with 860 mm of rain recorded at Centre Island in four days.
Sandy continued to move west-northwest until it reached landfall at Port Roper. Trawlers sheltering in the Roper River suffered damage and reported the passage of an eye in which calm winds were experienced for about one hour. The cyclone weakened to a depression by 1800 UTC 25 March but could be identified for a long period as it moved westward into the Indian Ocean.