The El Niño–Southern Oscillation (ENSO) remains neutral — neither in an El Niño nor La Niña phase, says the Australian Government Bureau of Meteorology (BOM) in its latest report. Climate models favour ongoing neutral conditions for the southern hemisphere winter, despite continued warming of the tropical Pacific Ocean.
Key indicators of ENSO are mostly near average. Sea surface temperatures (SSTs) are close to the long-term average across the tropical Pacific Ocean, with Nino3.4 positive for the first time since mid-August 2017.
Waters beneath the surface are slightly warmer than average. In the atmosphere, the Southern Oscillation Index (SOI) and trade winds are both within the neutral range.
Models suggest further warming of the tropical Pacific Ocean is possible over the coming months, with two of eight models indicating an El Niño could develop after the southern winter. However other models fall well short of El Niño thresholds, resulting in a broad range of possible scenarios for spring.
When ENSO is neutral it has limited influence on Australian and global climate. During an El Niño, eastern Australia typically sees less rainfall than usual during winter and spring.
The Indian Ocean Dipole (IOD) is currently neutral, with most climate models indicating a neutral pattern is likely to persist through the southern winter.
However, there is a lot of variation amongst models in their outlooks, with one (of six models) forecasting a positive IOD to develop in winter, and another predicting a negative IOD during spring.
The accuracy of IOD event forecasts is lower at this time of the year.
