Tropical Climate Update

Heavy rainfall from tropical cyclone Owen

During the past week, tropical cyclone Owen impacted parts of the northeastern Northern Territory and Queensland, producing very large rainfall totals in some locations. Owen re-developed as a tropical cyclone over the central Gulf of Carpentaria on 11 December while tracking westwards towards the Gulf coast of the Northern Territory. It briefly crossed the southern Gulf coast at a sparsely populated location to the west of Borroloola in the NT as a severe tropical cyclone (category 3), then made a U-turn and moved eastwards across the southern Gulf waters. Fortunately, Owen's second landfall, at category 3 strength, was also at a sparsely populated location, north of Gilbert River Mouth on the west coast of Cape York Peninsula. While peak wind gusts at the time of both landfalls were estimated to be in excess of 165 km/h, no significant infrastructure damage was reported.

After dropping below tropical cyclone strength, ex-tropical cyclone Owen moved across the Cape York Peninsula and upon reaching Queensland's east coast, adopted a southerly track, roughly parallel to the coast. While wind speeds had significantly decreased, Owen remained a significant hazard due to the heavy rainfall it generated. The highest totals were recorded along the coast and adjacent inland between the Cairns and Mackay regions. Widespread rainfall totals above 200 mm fell during the event with much higher totals at some locations along the north tropical coast. At Halifax, near Lucinda, a daily rainfall total of 681 mm was recorded, the highest 24-hour rainfall total ever recorded in Australia during the month of December. Ex-tropical cyclone Owen continues to weaken and is not expected to re-develop significantly in the coming days.

Moisture associated with Owen was also drawn into a weather system which affected the remainder of the Australia's east coast generating widespread fainfall of the order of 100-200 mm, from the coastal Capricornia district of Queensland to southern New South Wales, much of Victoria and eastern Tasmania. 

Owen developed in an environment which was made favourable for tropical cyclone formation by very warm waters in the Gulf of Carpentaria and deep moisture associated with cross-equatorial wind-flow feeding into a trough associated with Owen and another nearby tropical low. As Owen strengthened, this trough deepened significantly, but the upper-level flow identified with a monsoon trough failed to evolve. As such, a true monsoonal flow did not develop across northern Australia during this event.    

Following the passage of Owen across the Gulf of Carpentaria, significant cooling of Gulf waters occurred, reducing sea surface temperatures to near average after being close to 2 °C above average just before Owen re-developed.

 Madden–Julian Oscillation over Maritime Continent

In recent days, a moderate strength pulse of the Madden–Julian Oscillation (MJO) moved into the Maritime Continent, north of Australia. At this time of the year, an MJO in this region typically leads to enhanced rainfall across northern Australia and the Maritime Continent. After experiencing relatively dry conditions in recent months, significant rainfall totals in parts of Papua New Guinea were reported during the past week. An MJO pulse can also aid the development of the monsoon over northern Australia, leading to widespread, heavy rainfall. Under the right circumstances, an MJO in the region can also significantly increase the likelihood of tropical cyclone formation, although no tropical cyclones are currently forecast to affect the Australian region in the coming week.

In the last couple of days tropical cyclone Kenanga developed over the Indian Ocean, just west of the Australian region. This system is expected to intensify and move further away from Australia in the coming days, remaining over the western Indian Ocean.

The MJO is forecast to maintain similar strength and track further east across over the Maritime Continent, increasing the likelihood of monsoon development in the coming fortnight. However, current weather models do not suggest monsoonal flow will develop in the coming week.

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

Further information on TC Kenanga is available via the La Reunion RSMC forecasting service.