Climate outlook for October to December

Issued 28 September 2017

Climate outlook overview

The October to December outlook, issued 28 September 2017, shows an equal chance of wetter or drier conditions for most of Australia.
October is likely to be wetter than average for large parts of eastern and central mainland Australia, but drier for western WA.
October to December daytime and night-time temperatures are likely to be warmer than average for most of tropical northern Australia and parts of southeast Australia. Nights are likely to be cooler around the Great Australian Bight. Elsewhere, chances of warmer or cooler nights are roughly equal.
Climate influences from the Indian and Pacific oceans are likely to be competing, with a slightly drying influence in the Indian Ocean likely to be cancelling out a slightly wetter influence from the Pacific Ocean. See the Climate Influences section for more information.

Chances of a wetter or drier October to December for Australia are roughly equal.
While the overall three-monthly signal is neutral, October is likely to be wetter than average for central and eastern mainland Australia, and drier for western WA. This wet signal is likely to be driven by more localised weather events.
Climate influences from the Indian and Pacific oceans are likely to be competing, with a slightly drying influence in the Indian Ocean likely cancelling out a slightly wetter influence from the Pacific Ocean.
Historical outlook accuracy for October to December is moderate for most of Australia, but low in parts of the southern mainland, southern Queensland and parts of the tropical north. See map for more detail.

October to December daytime and night-time temperatures are likely to be warmer than average for tropical northern Australia, western WA, the Queensland coast, and parts of southeast Australia. Nights are likely to be cooler around the Great Australian Bight. Elsewhere, chances of warmer or cooler days and nights are roughly equal.
For October, cooler nights are likely for southern WA, most of SA, and western NSW. Warmer October nights are more likely in eastern Victoria, Tasmania and northern Australia.
Historical accuracy for maximum temperatures is moderate to high over most of Australia, except for a small area in western WA, where accuracy is low. Minimum temperature accuracy is moderate over much of the country, but patchy along parts of the east coast and the northern tropics.

The El Niño–Southern Oscillation (ENSO) is neutral, but tropical Pacific Ocean temperatures have been cooling since mid-winter. Forecasts suggest that Pacific sea surface temperatures may approach La Niña thresholds towards the end of 2017. Typically La Niña brings wetter conditions to much of northern and eastern Australia during spring, with the wetter influence contracting further to the northeast in the summer months.
The Indian Ocean Dipole (IOD) remains neutral, but patterns in the broader Indian Ocean may act to draw moisture away from Australia.
These influences from the Indian and Pacific oceans are likely to be competing, with a slightly drying influence in the Indian Ocean likely to be cancelling out a slightly wetter influence from the Pacific Ocean.
In addition to the natural drivers such as the El Niño–Southern Oscillation and the IOD, Australian climate patterns are being influenced by the long-term increasing trend in global air and ocean temperatures.
Bureau climatologists continually monitor the climate for any significant developments, with information on El Niño/La Niña and IOD events available fortnightly via the ENSO Wrap-Up. For a summary of Pacific and Indian Ocean outlooks, please see the Climate Model Summary.