MELBOURNE, Australia — The tropical Pacific Ocean continues developing towards El Niño, while in the Indian Ocean, a positive Indian Ocean Dipole (IOD) is underway.
The Bureau’s ENSO Outlook remains at El Niño Alert, meaning there is approximately a 70% chance of El Niño occurring in the coming months; about triple the normal likelihood.
Ocean temperature patterns in the Indian Ocean have been at positive IOD levels now for two months. As a result, 2018 will be considered a positive IOD year.
A positive IOD during spring increases the chance of below average rainfall for southern and central Australia, and can reinforce the effects of a developing, or fully formed, El Niño. El Niño effects in Australia over summer include higher fire risk, greater chance of heatwaves, and fewer tropical cyclones.
Sea surface temperatures in the tropical Pacific Ocean have warmed to El Niño levels over the past fortnight. However, atmospheric indicators of El Niño are largely near normal, suggesting that the ocean and atmosphere are not yet reinforcing each other, or ‘coupled’. This reinforcement is critical in any El Niño developing and becoming self-sustaining.
International climate models suggest further warming of the tropical Pacific Ocean is likely, increasing the possibility of coupling occurring in the coming months. Seven out of eight climate models suggests sea surface temperatures will remain above El Niño thresholds until at least March 2019.
Model outlooks suggest the positive IOD will decay during November. IOD events typically have little influence on Australian climate from December to April.
