MELBOURNE, Australia – The El Niño–Southern Oscillation (ENSO) is currently neutral, reports the Bureau of Meteorology of the Australian Government in its latest update. Sea surface temperatures (SSTs) in the central equatorial Pacific Ocean are ENSO-neutral, having gradually cooled from El Niño levels since December 2023.
This cooling is being sustained by deep waters surfacing in the central and eastern Pacific. However, the extent and magnitude of cool water has decreased since last fortnight. Atmospheric patterns, including cloud and trade winds, are currently 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, with a fourth just briefly reaching the threshold; the remaining 3 models suggest SSTs are likely to remain at ENSO-neutral values (between −0.8 °C to +0.8 °C ) throughout the forecast period. The ENSO Outlook remains at La Niña Watch. La Niña Watch does not guarantee La Niña development, only that there is about an equal chance of ENSO remaining neutral or La Niña developing during the remainder of 2024.
The Indian Ocean Dipole (IOD) is currently neutral. In recent weeks, the east Indian Ocean has cooled, with the latest weekly IOD index value (as of 18 August) of +0.33 °C. However, most models indicate that the IOD is likely to remain neutral until at least the end of Austral 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 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 negative (as at 17 August). The index is forecast to become neutral during the coming week. During winter, a negative SAM typically increases the likelihood of rain-bearing fronts across southern Australia and decreases rainfall influenced by onshore flow in parts of the east.
A moderate pulse of the Madden–Julian Oscillation (MJO) is currently in the Indian Ocean (as at 17 August). Models suggest the pulse will become weak as the MJO progresses to the Maritime Continent over the coming week. When the MJO is in the Indian Ocean at this time of year, it typically decreases rainfall over southern Australia.
