Issued: Tuesday, 15 August 2023
The Bureau of Meteorology remains at El Niño Alert in the latest Climate Driver Update and continues to forecast warmer and drier conditions for the coming months.
The latest long-range forecast for September to November shows rainfall is likely to very likely (60% to greater than 80% chance) to be below average for much of the eastern half of Australia and southern Western Australia.
Higher than usual maximum temperatures are very likely (greater than 80% chance) for almost all of Australia.
Bureau of Meteorology Senior Climatologist Catherine Ganter said the atmospheric changes we would expect to see during El Niño had so far not occurred.
“Atmospheric indicators of El Niño include wind, cloud and broad-scale pressure patterns across the Pacific Ocean,” Ms Ganter said.
“While the past fortnight has seen a decrease in Southern Oscillation Index (SOI) values to El Niño-like values, this strong swing has been due to more localised higher than average pressure in Darwin, rather than a broader El Niño signal.”
“Overall, the atmospheric indicators suggest the Pacific Ocean and atmosphere are not yet consistently reinforcing each other as occurs during El Niño events.”
The status of the El Niño– Southern Oscillation (ENSO) Outlook is determined using set Criteria and expert analysis by climatologists at the Bureau.
“There is no single definitive index or measure for the ENSO,” Ms Ganter said.
“It is a complex phenomenon that describes changes in the Pacific Ocean and the atmosphere above it.”
The US, Japan and Australia each have slightly different metrics for monitoring and declaring ENSO events.
The Bureau issued an El Niño Watch on 14 March 2023, and the ENSO Outlook moved to El Niño Alert on 6 June this year.
When El Niño Alert criteria have been met in the past, an El Niño event has developed around 70 per cent of the time.
Each El Niño event is different and its impact can vary.
During El Niño, the chance of drier conditions increases for eastern Australia during winter and spring and it is usually warmer for the southern two-thirds of Australia.
In summer, El Niño increases the likelihood of reduced rainfall in northern Australia. El Niño summers also tend to have warmer days across northern and south-eastern Australia, as well as parts of the south-west.
El Niño events increase the risk of extreme temperatures, like heatwaves and hotter days.
Ms Ganter said global sea surface temperatures were the highest on record (since 1900) for their respective months during April to July 2023.
“We haven’t seen an El Niño develop with ocean temperatures broadly this warm. Some of the things that we’ve understood about how they operate in the past, may not operate that way in the future,” she said.
“We are keeping a really close eye on this and are regularly monitoring conditions in the tropical Pacific Ocean.”
