Climate outlook for September to November
Issued 27 August 2015
Climate outlook overview
- A wetter-than-average spring is more likely in western and central Australia, while in the east and north there is an equal chance of above or below average rainfall. Warmer nights are likely for most of Australia, with warmer days likely along the east coast and far southwest WA.
- The current outlook reflects the record warm sea surface temperatures in the Indian Ocean, and the El Niño in the Pacific (see the climate influences section for more information).
Wetter in the west and centre
- There is an increased chance of a wetter-than-average season over much of southern and central WA, the southern NT, SA and extending into parts of western NSW Victoria and Queensland. In far north Queensland, spring is likely to be drier than average. Most of eastern Australia has a roughly equal chance of a wetter or drier season.
- The current outlook reflects the record warm sea surface temperatures in the Indian Ocean, and a strengthening El Niño in the Pacific.
- Historical outlook accuracy for spring is moderate to high over most of Australia.
Warmer spring nights for most of the country
- Spring days are likely to be warmer than average along the east coast and in far southwest WA. Small parts of WA and much of Victoria are likely to have cooler than normal spring days. Overnight temperatures are likely to be warmer than normal across much of the country except in the southeast where the chances are roughly equal.
- Significantly warmer-than-average sea surface temperatures in the Indian Ocean and nearer the Australian coastline are likely influencing the warmer overnight temperatures expected for much of the country.
- Maximum temperature accuracy is moderate to high over most of Australia, except for some small patches in WA, where accuracy is low to very low. Minimum temperature accuracy is moderate over much of the country but patchy in WA and parts of the northern tropics.
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 the record warm sea surface temperature (SST) pattern in the Indian Ocean is producing roughly equal chances of a wetter or drier three months in the eastern half of the country, and increasing the chances of above-average rainfall across WA, SA and central Australia. 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.
- 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 the following autumn, the typical El Niño-Southern Oscillation transition period.
- The Indian Ocean Dipole (IOD) is currently neutral. Three out of five international models suggest an increased chance of a positive IOD event developing during spring, with the other two maintaining mostly neutral outlooks. Recent values of the index have been near the positive IOD threshold, however these values would have to be sustained for several more weeks for a positive IOD event to become officially established. 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.
- 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.
