MELBOURNE, Australia – Sea surface temperatures (SSTs) in the central equatorial Pacific Ocean are ENSO-neutral, having gradually cooled from El Niño levels since December 2023, reports the latest update from the Bureau of Meteorology of the Australian Government. This cooling is being sustained by deep waters surfacing in the central and eastern Pacific. Atmospheric patterns, including cloud and trade winds, remain largely ENSO-neutral.
Three of 7 climate models suggest the possibility of SSTs in the tropical Pacific exceeding the La Niña threshold (below −0.8 °C) from October, while the remaining 4 models, including the Bureau’s, suggest SSTs are likely to remain at ENSO-neutral values (between −0.8 °C to +0.8 °C ) throughout the forecast period. This means it is possible a La Niña may develop in coming months.
The Indian Ocean Dipole (IOD) is currently neutral, with the latest weekly IOD index value (as of 1 September) of +0.15 °C. Most models indicate that the IOD is likely to remain neutral until at least the end of spring.
Global SSTs were the warmest on record for each month between April 2023 and June 2024. July 2024 global SSTs were the second warmest on record, not as warm as July 2023 but much warmer than any other year. August 2024 is currently tracking as the second-warmest August for SSTs on record. The current global pattern of warmth differs to historical patterns of SSTs associated with ENSO and IOD. This means future predictions of ENSO and IOD based on SSTs during past events may not be reliable. Phenomena such as ENSO and the IOD are only broad indicators of the expected climate. The long-range forecast provides better guidance on local rainfall and temperature patterns.
The Southern Annular Mode (SAM) is currently positive (as at 1 September), having been neutral for most of the second half of August. The SAM index is forecast to become neutral during the coming week. A neutral SAM has no strong influence on Australian rainfall and temperature patterns.
A pulse of the Madden–Julian Oscillation (MJO) is currently in the Maritime Continent region to Australia’s north (as at 1 September). Most models suggest the pulse will either maintain its strength or strengthen slightly as the MJO progresses over the Maritime Continent in the coming week. When the MJO is in the Maritime Continent at this time of year, it may contribute towards strengthening trade winds, which can assist with La Niña development.
