Tropical Climate Update

Dry and warm monsoon break for northern Australia

Following the tropical activity associated with ex-tropical cyclone Gretel, in the second week of March, the monsoon trough and related monsoon conditions dissipated over northern Australia. In place of the monsoonal westerly flow, trade flow (south-easterly winds) became the dominant wind pattern over tropical Australia. Typically, trade winds are associated with stable weather over northern Australia, with generally dry conditions affecting most regions, apart from the Queensland east coast, where onshore easterly winds provide humidity for potential rainfall. The trade wind regime is the typical wind pattern during northern Australia's dry season.

The climate outlook indicates lower than normal rainfall is likely over much of northern Australia for the next week or two. At this time of the year, south-easterly winds are generally also associated with above-average temperatures. The outlook for temperature, shows that northern Australia has a very high likelihood of above-average daytime and overnight temperatures in the coming weeks.

Madden–Julian Oscillation contributes to dry and warm outlook for northern Australia

The Madden–Julian Oscillation (MJO) is currently over the Indian Ocean and tracking eastwards towards the Australian region. The MJO became moderately strong while tracking over the Indian Ocean during the past week and, at this time of the year, that typically leads to an increase in easterly winds and reduced rainfall over northern Australia. 

Climate models agree the MJO will weaken as it approaches the Australian region. There is some variation amongst the model guidance as to how rapidly the MJO pulse weakens, but it is expected to be weak or indiscernible within the next week to ten days, prior to moving into the eastern Maritime Continent.

As a result, while the drying influence of the MJO is expected to reduce in the coming week, beyond this timeframe models do not suggest a significant increase in the chance of above-average, widespread rainfall. This would also suggest that the MJO is not likely to be associated with renewed monsoon activity or a significant increase in tropical cyclone risk across waters to Australia's north in the coming fortnight.

In the local domain, however, current weather charts show that a trough has developed in the easterly flow over the Coral Sea and, as this approaches Australia, significant rainfall is expected over parts of the far north in the coming week.

If the MJO does maintain significant strength, as some models indicate, or becomes stronger than forecast over Australian longitudes, there would be an increased chance of enhanced rainfall and likelihood of monsoonal conditions developing across the region in two to three weeks.

Read more about the Madden–Julian Oscillation