Tropical Climate Update

Three tropical cyclones active in the Australian region at the same time

As severe tropical cyclone Marcus moved away from Australia over the Indian Ocean during the past week, the monsoon trough over the Arafura and Coral seas reorganised and became more active. Tropical cyclone Nora developed from a low in the Arafura Sea on 23 March, then tracked south into the Gulf of Carpentaria and intensified to a category 3 severe tropical cyclone, with peak sustained winds estimated at 155 km/h. Nora made landfall on the west coast of the Cape York Peninsula, between Cape Keerweer and Porumparaaw, as a category 3 system, on the night of 24 March. Significant vegetation damage and minor infrastructure damage was reported at Porumparaaw. The tropical moisture associated with Nora contributed to widespread flooding rains across much of Far North Queensland, including parts of the east coast around Cairns. Several locations observed daily rainfall totals of more than 300 mm to 9 am on 26 March, with Port Douglas registering a staggering 593 mm in 24 hours. Further widespread falls to 200 mm, with a peak rainfall total of 499 mm, were observed in the 24 hours to 27 March. Fortunately, the rainfall focus was about 200 km south of the Port Douglas region.

As Nora approached the west coast of Far North Queensland, and Marcus tracked parallel to the Western Australian coastline in the Indian Ocean, tropical cyclone Iris briefly became the third cyclone to be simultaneously active in the Australian region. Iris reached tropical cyclone intensity while in Fiji's area of responsibility in the Coral Sea, but briefly moved into Queensland's region as a category 1 tropical cyclone, before weakening to below cyclone intensity.

Ten tropical cyclones in Australian region so far this season

After a busy week, Australia has now observed ten cyclones during the 2017-18 tropical cyclone season, to date. This is just short of the long-term average number of eleven tropical cyclones per season across the Australian region. The tropical cyclone season runs until 30 April, so there remains a reasonable likelihood of exceeding the average number—something that has not been achieved since 2005-06.

Western Australia has seen the majority of tropical cyclones, with the first seven systems of the season affecting that region. Since mid-March, the Northern Territory and Queensland have both had two tropical cyclones in their region. Marcus moved through both Western Australia and the Northern Territory, giving a total of ten systems for the Australian region.

Of the ten systems, three have become severe tropical cyclones (category 3 or stronger), with Marcus the strongest, attaining the rare status of category 5 intensity, with sustained maximum winds estimated at more than 230 km/h while passing over the Indian Ocean.

For up-to-date tropical cyclone information for the Australian region, including daily cyclone outlooks, please visit the Bureau's current tropical cyclones webpage.

Tropical wave activity moves away from the Australian region

A pulse of the Madden–Julian Oscillation (MJO) near the Maritime Continent remains relatively weak, however indicators suggest it recently facilitated favourable atmospheric conditions for enhanced convection across northern Australia. Equatorial Rossby waves, westward moving tropical pulses of low pressure, were a significant feature in the Australian region in the last fortnight. These tropical atmospheric waves provide favourable conditions for enhanced tropical convection and tropical cyclone formation in the region they affect.

Most international climate models suggest the MJO pulse will strengthen and move over the Western Pacific region in the coming week. It is forecast to maintain an easterly track for the next fortnight, suggesting climate conditions will become less favourable for enhanced convection and rainfall across Australia and the Maritime Continent during that period.

See the Bureau's current MJO monitoring for more information.