Tropical Climate Update

A monsoon trough and heavy rainfall over northern Australia

During the past week, a monsoon trough has extended from the eastern Indian Ocean across northern Australia, bringing heavy rainfall to the region Rainfall totals for the week ending 9 am on 24 March exceeded 200 mm in the north Kimberley coast in Western Australia, the Top End coast of the Northern Territory, and the western parts and the Tropical North of Queensland. The coast between Townsville and Cairns recorded weekly totals over 300 mm. The highest weekly total, to 9am on 24 March, was 1037.6 mm at Cardwell Range in Queensland, which also included the highest daily total of 402.8 mm on 20 March.

Tropical moisture associated with the monsoonal flow has been drawn into central and western Queensland by a surface trough from 22 March, enhancing thunderstorms and showers. This is expected to persist in the vicinity of the monsoon trough over northern Australia and into western and southern Queensland for the coming days.

Fortnightly forecast

For the coming fortnight beginning 29 March, rainfall is likely to be above average across northern Australia. There is an increased chance of unusually wet conditions in the north of Western Australia, much of the Northern Territory and Queensland for the fortnight. Unusually wet refers to rainfall totals in the highest 20% of March–April fortnights between 1981 and 2018.

There is an increased chance of unusually cool maximum temperature in northern Australia, associated with likely wet conditions. Unusually cool maximum temperatures are defined as those in the lowest 20% of March–April daytime temperatures between 1981 and 2018. This is in contrast to the first half of March when maximum temperatures were 2 to 6 °C above average in the northern tropics, and up to 8 °C above average further south as heatwave conditions persisted across central Australia.

Tropical lows in the Indian Ocean

A tropical low (27U) formed in the vicinity of a monsoon trough, to the north of Karratha in the Pilbara region of Western Australia on 24 March. Tropical low (27U) moved south-west and is currently, as of 25 March, located well off the north-west Pilbara coast.  Tropical low (27U) is forecast to track west away from the Western Australia mainland.

A weak tropical low (28U) may develop near the west Kimberley coast in Western Australia. The chance of 28U developing into a tropical cyclone remains low.  

For the latest information see the Bureau's 7-day tropical cyclone forecast.

Madden–Julian Oscillation lingering in western Pacific

During the past week (to 25 March), the Madden-Julian Oscillation (MJO) moved east across the Indian Ocean and the Maritime Continent into the Western Pacific and weakened. The majority of forecast models indicate a weak MJO pulse will linger in the Western Pacific until the end of March. Some models forecast a strengthening of the MJO while over the western or central Pacific region. At this time of year, an MJO pulse in the Western Pacific, may contribute to an increased chance of rainfall across northern Australia. Other tropical wave activity currently in the area is likely to enhance the probability of above-average rainfall across northern Australia. There remains an increased risk of further tropical low and cyclone development while the monsoon trough and MJO remain active.