Tropical Cyclone Sid

24 - 28 December 1997


An active phase of the intraseasonal oscillation late in December and early January resulted in the formation of five cyclones: Sid, Selwyn, Ron, Susan and Katrina , across the Australian and southwest Pacific Ocean tropical cyclone basins. Sid was the first of these to develop as a cross-equatorial surge resulted in the formation of the monsoon trough near northern Australia. Sid developed very close to the Northern Territory's north coast near Darwin before moving east along the coast, then south into the Gulf of Carpentaria before decaying. The remnant low produced record and devastating flooding two weeks later around Townsville in North Queensland.

A low pressure system over the northwest of the Northern Territory moved just offshore into the Timor Sea. Interaction with monsoon westerlies then steered the low eastward along the coast with Sid forming on 26 December in the Arafura Sea, 70 km from the Northern Territory coast. Further intensification was restricted by the proximity to the coast. The cyclone reached the edge of the Gulf of Carpentaria on 27 December after passing close to the town of Nhulunbuy. It then took a south-southeast course into the Gulf of Carpentaria as the system came under the influence of a high amplitude middle level ridge in the Coral Sea. Sid briefly intensified early on 28 December in the central Gulf reaching a maximum sustained wind speed of 26 m/s. It then weakened below cyclone intensity under the influence of upper level shearing as it approached the southern Gulf coast late on 28 December.

As Sid passed the township of Nhulunbuy and Groote Eylandt trees were uprooted and powerlines were damaged at both locations. Two craft dragged their moorings and one was washed against rocks at Nhulunbuy Yacht Club.

Over the week and a half following Sid 's decay the remnants meandered about the Top End of the Northern Territory and Gulf of Carpentaria without redeveloping into a cyclone. The low finally moved into Queensland in early January.

Whilst remaining near stationary near Townsville the low acted as a focal point within the monsoon trough, bringing heavy rainfall to North Queensland and causing major flooding. Townsville recorded 549 mm of rain in the 24-hour period ending 2300 UTC 10 January, with another 245 mm falling during the next two days. Included in the first days rainfall was a total of 120.6 mm in one hour and 205.2 mm in two hours.

The flooding resulted in the loss of one life when a man was drowned after his car was washed off a creek crossing in Townsville. In Townsville around 100 houses had substantial over-floor flooding with hundreds more sustaining property flooding. Numerous cars were damaged by flooding, and up to 50 per cent of the houses in Townsville lost power at some stage. Damage to local Government infrastructure was high. On Magnetic Island just offshore from Townsville, a landslide caused major damage to a tourist complex. The small communities of Black River and Bluewater north of Townsville suffered extensive damage from flash-flooding. Forty-eight houses were affected in this area with the majority rendered uninhabitable. Fourteen of these were totally destroyed with eight washed away. One hundred houses experienced over-floor flooding in the towns Halifax and Ingham north of Townsville. There was also extensive damage to the rural sector.

Wave action and storm surge inflicted severe damage and erosion to coastal areas around Townsville with damage from these effects quoted as reaching A$19m. The sea reached a level just below highest astronomical tide level at 2220 UTC 10 January and the Townsville wave recording station recorded a maximum significant wave height of 5.41 metres at 0500 UTC 10 January. Seven vessels sank in Townsville harbour. The total damage bill was estimated to be well in excess of A$100m.

Track and intensity

All times in CST.

Best Track of Tropical Cyclone Sid