MELBOURNE, Australia – The El Niño–Southern Oscillation (ENSO) is currently neutral, reports the Bureau of Meteorology of the Australian Government in its latest update. However, the Bureau’s ENSO Outlook is at La Niña Watch, due to some early signs that an event might form in the Pacific Ocean later in 2024. A La Niña Watch does not guarantee that a La Niña will develop.
There is about an equal chance of neutral ENSO conditions in the same outlook period.
Sea surface temperatures (SSTs) in the central Pacific have been steadily cooling since December 2023. This surface cooling is supported by a significant amount of sub-surface cooling in the central and eastern Pacific. Recent cloud and surface pressure patterns are ENSO-neutral.
Climate models suggest that SSTs in the central tropical Pacific are likely to continue to cool over the coming months. Four of seven models suggest SSTs are likely to remain at neutral ENSO levels, with the remaining three models showing SSTs cooling to La Niña levels from August.
It is important to emphasise that early signs of La Niña are most relevant to the climate of the tropical Pacific, and that the long-range forecast for Australian rainfall and temperature provides better guidance for local climate.
The Indian Ocean Dipole (IOD) is currently neutral. The most recent 4 weeks have seen the IOD index within neutral thresholds, with the latest week just below the positive IOD threshold (+0.40 °C). Predictability of the IOD is low at this time of year.
Global sea surface temperatures (SSTs) have been the warmest on record for each month between April 2023 and April 2024, with May 2024 SSTs on track to exceed May 2023. The global pattern of warmth is affecting the typical historical global pattern of sea surface temperatures associated with ENSO and IOD. As the current global ocean conditions have not been observed before, historical comparisons based on past ENSO or IOD events may not be reliable.
The Southern Annular Mode (SAM) is currently negative (as at 25 May). Forecasts indicate the index is expected to remain negative during the first two weeks of June.
The Madden–Julian Oscillation (MJO) is currently moderately strong and located in the eastern Indian Ocean. The majority of models forecast that the MJO will track towards the Maritime Continent region by the end of May.
