Climate outlook for October to December
Issued 24 September 2015
Climate outlook overview
- October to December likely to be wetter than average in southwestern and central Australia; drier than average in parts of the southeast and northeast.
- Warmer nights are likely for most of Australia; warmer days along parts of the southern and eastern coasts.
- A very warm Indian Ocean, and a mature El Niño in the Pacific are influencing this outlook (see the climate influences section for more information).
Wetter in the southwest and centre; drier in parts of the east
- October to December is likely to be wetter than average over southern WA, most of the NT, SA, and southwest Queensland. Conversely, the northern Cape York Peninsula in Queensland, eastern Victoria and southeast NSW are likely to be drier than average. Elsewhere, the chances of a wetter or drier three months are roughly equal.
- For October, places which are likely to have a drier than average month include the tropical north, parts of the Pilbara in WA, southern Victoria and northern Tasmania.
- The current outlook reflects a combination of very warm sea surface temperatures in the Indian Ocean, and a mature El Niño in the Pacific.
- Historical outlook accuracy for October to December is moderate over most of Australia.
Warmer nights for most of the country
- Daytime temperatures for October to December are likely to be warmer than average along the southern coastline, extending from Geraldton in WA, across to the Eyre Peninsula in SA. Much of the east coast south of Mackay is also likely to be warmer than average. Daytime temperatures are likely to be cooler than average in an area spanning northern WA and the central NT.
- Overnight temperatures are likely to be warmer than normal across most of the country except in the southeast and parts of the tropical north, where the chances are roughly equal. Across the southwest of Australia, extending into SA, there is a strong likelihood of above normal night-time temperatures (greater than 80% chance in places).
- The current outlook reflects a combination of very warm sea surface temperatures in the Indian Ocean, and a mature El Niño in the Pacific.
- Maximum temperature accuracy is moderate to high over most of Australia, except for a small area in far west WA, where accuracy is low to very low. Minimum temperature accuracy is moderate to high over much of the country but patchy in the northern tropics, and parts of the east coast.
Climate influences
- El Niño persists in the tropical Pacific Ocean. El Niño is usually associated with below-average winter–spring rainfall over the eastern half of Australia, with 17 of the 26 events since 1900 resulting in widespread drought for Australia. However, the combination of El Niño with warmer-than-average sea surface temperatures (SSTs) in the Indian Ocean is producing roughly equal chances of a wetter or drier three months across most of the eastern States, and increasing the chances of above-average rainfall across WA, SA and central Australia.
- Climate models suggest that El Niño is likely to peak towards the end of 2015, weakening in the first quarter of next year. At this time of year, models have little skill forecasting beyond autumn, the typical El Niño-Southern Oscillation transition period.
- The Indian Ocean Dipole (IOD) is nearing the criteria needed to label 2015 a positive IOD year. Four out of five international models suggest an increased chance of a positive IOD persisting through to at least November. Positive IOD events are typically associated with decreased winter–spring rainfall over southern and central Australia, however the widespread warmth across the Indian Ocean basin may offset this historical influence.
- This pattern of SSTs in the Pacific and Indian oceans partially resembles the 1997–98 El Niño, also a strong event, but with only minor impacts on Australian rainfall patterns. The combination of a warm tropical Pacific and warm Indian Ocean represents an unusual set of circumstances.
- 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.
