There is uncertainty over the potential strength of the El Niño that will likely emerge this year. According to the Australian Bureau of Meteorology (BoM), model forecasts range from a weak-to-moderate event to the possibility of a strong event, based on the level of warming in the central tropical Pacific (relative Nino3.4 index).
“A strong El Niño signal in the Niño3.4 region doesn’t necessarily mean strong impacts ... ENSO (El Nino-Southern Oscillation) is only one of many factors that can influence Australia’s seasonal weather and climate,” it said in its latest climate driver update.
All models, including the BoM’s, forecast the tropical Pacific to continue warming in the coming months, reaching El Niño thresholds later in the year. “There is some variation across models in the rate at which El Niño thresholds may be reached, with some suggesting development as early as May, while others show a slower warming with thresholds not being met until July,” the weather agency said.
It said ocean temperatures around Australia are mixed, with cooler waters in some regions and warmer waters along the east coast. The Pacific is neutral, but the heat is brewing. “Forecasts point to warmer seas in the future, which could mean more rain and possibly an El Nino later this year,” said BoM.
Warmer SSTs
Sea Surface Temperature (SST) forecasts for May to July indicate warmer-than-average waters around much of Australia, with temperatures up to 2°C warmer than average in the Tasman Sea. Warmer waters can increase the potential moisture and energy available for rain systems.
The report says the El Niño–Southern Oscillation (ENSO) is neutral now. The latest Niño-3.4 index value for the week ending 26 April 2026 is 0.23°C, within the ENSO-neutral range (−0.80 to +0.80°C).
The region has warmed in recent weeks, with the index warming 0.5°C over the past fortnight. The recent warming in the sub-surface indicates that the SSTs are likely to warm further in the coming weeks.
Atmospheric indicators, including trade winds, pressure and cloud patterns across the tropical Pacific, remain consistent with ENSO-neutral conditions.
The Madden-Julian Oscillation is likely to cross the Indian Ocean in the next few days and could re-intensify around mid-May over the Western Hemisphere region. If this occurs, the associated westerly wind anomalies over the western Pacific could favour further warming of the tropical Pacific.
Southern Oscillation Index
As of April 26, 2026, the 30-day Southern Oscillation Index (SOI) is −10.6, with the recent drop in the index reflecting the shift from monsoonal conditions to a period of more settled weather and above-average pressure in Darwin. The 60-day and 90-day SOI index values are +2.5 and +6.2, respectively.
The Southern Oscillation Index (SOI) measures the large-scale fluctuations in air pressure between Tahiti (central Pacific) and Darwin, Australia (western Pacific), and is an indication of the atmospheric component of El Niño–Southern Oscillation (ENSO). Negative values indicate El Niño (warmer ocean) and positive values indicate La Niña (cooler ocean).
IOD neutral
The Indian Ocean Dipole (IOD) is neutral. As of 26 April 2026, the IOD index is +0.09°C. Models indicate the IOD is most likely to remain neutral until the end of autumn, with a positive IOD possible during winter–spring.
Some models show it could develop earlier, in late autumn. However, the forecast uncertainty associated with the IOD is high at present, with models having a large spread of possible outcomes.
The Southern Annular Mode (SAM) index is neutral as of 26 April 2026. It is forecast to remain mostly neutral over the coming fortnight, the report noted.
The Southern Annular Mode is the main climate pattern of the Southern Hemisphere, describing the north-south movement of westerly winds between the mid-latitudes and Antarctica.
Published on April 29, 2026