Tropical Cyclone Seth

23 December 2021 - 7 January 2022

Tropical Cyclone Seth was a tropical cyclone for a little over 24 hours in the Coral Sea but its entire track lasted 15 days. The most significant impacts were severe flooding in southeast Queensland and hazardous surf along the southern Queensland and northern New South Wales coast. The low was responsible for onset of the monsoon over Darwin and the Top End.

The system originated north of the Northern Territory in the eastern Timor Sea on 23 December and moved south, passing just to the west of the Tiwi Islands on Christmas Day before crossing the coast near Dundee Beach southwest of Darwin early on 26 December. The low was slow moving before tracking east over land into the Gulf of Carpentaria on 28 December then over Cape York Peninsula on 29 December and into the Coral Sea on 30 December.

Tropical cyclone intensity is estimated on the morning of 31 December, peaking at category 2 intensity later that day based on observations at Frederick Reef where wind gusts peaked at 82 kn (152 km/h) at 1908 AEST 31 January (AEST=UTC+10 hours). Gale-force winds were recorded at Marion Reef, Frederick Reef and Cato Island, while storm-force winds were recorded at Frederick Reef.

On 2 January, Seth was reclassified as a sub-tropical system but still produced gales until later on 3 January. A strong circulation continued on following days as it moved slowly to the northwest then west crossing the southern Queensland coast on 7 January near Hervey Bay. The system then weakened overland but not before producing extreme rainfall in the area.

The most significant hazards during this event were:

Heavy rainfall and associated flooding in southeastern Queensland as the low moved over land. Intense flooding occurred on the Mary River. Daily falls exceeded 400 mm to 9am AEST on 8 January, including at Marodian 674 mm, Mt Kanigan 650 mm, Miva 572 mm and Glenwood 523 mm.

Hazardous surf and coastal inundation on southern Queensland and northern New South Wales coast on 2-5 January.

For more information see the TC Seth Report (pdf).

Track and intensity

Best Track of Tropical Cyclone Seth