MELBOURNE, Australia – El Niño remains strong, but continues its gradual decline. Climate models suggest a return to neutral levels in the second quarter of 2016. Close to the equator, the surface of the Pacific Ocean has now cooled by 0.5 °C since the El Niño peaked in late 2015.
Below the ocean surface, cooler than average waters now extend into the central tropical Pacific Ocean. In the atmosphere, trade winds have recently returned to near-normal levels in the central and eastern Pacific, although the Southern Oscillation Index (SOI) has been strongly negative in recent weeks.
During Australia’s northern wet season, it is not unusual to see big fluctuations in the SOI due to the passage of tropical systems, and hence its value may not be representative of the overall ENSO state.
Based on the 26 El Niño events since 1900, around 50% have been followed by a neutral year, and 40% have been followed by La Niña. Models suggest the neutral state is the most likely for the second half of 2016, followed by La Niña, with a repeat El Niño assessed as very unlikely.
Historically, the breakdown of strong El Niño events brings above average rainfall to some-but not all-parts of Australia in the first half of the year.
The Indian Ocean Dipole has little influence on Australian climate between December and April. However, Indian Ocean sea surface temperatures remain very warm across the majority of the basin which may provide extra moisture for rain systems across Australia.
