MELBOURNE, Australia – The El Niño–Southern Oscillation (ENSO) remains neutral, with sea surface temperatures (SSTs) in the central equatorial Pacific Ocean at ENSO-neutral levels, reports the Bureaus of Meteorology of the Australian Government in its latest update. Atmospheric indices, such as those related to patterns of surface pressure, cloud and trade winds, are broadly consistent with an ENSO-neutral state.
While some atmospheric indices have displayed La Niña-like signals over recent months, a consistent/sustained shift has not been observed.
The Bureau’s model suggests SSTs are likely to remain within the ENSO-neutral thresholds (−0.8 °C to +0.8 °C) throughout the forecast period to February 2025. Of the 6 other climate models surveyed, only one model suggests SSTs in the tropical Pacific are likely to exceed the La Niña threshold (below −0.8 °C) throughout November to February, which is sufficient time to be classified as a La Niña event. All models forecast neutral ENSO values by March.
The latest Indian Ocean Dipole (IOD) index value is −0.94 °C for the week ending 27 October, marking the fifth week close to or below the negative IOD threshold (−0.40 °C). All models indicate that the IOD index will meet or exceed negative IOD thresholds in November,
Global SSTs remain at near record levels, with temperatures since July being just short of the record temperatures observed during 2023, yet above all other years since observations began in 1854. The sustained nature of this significant global ocean heat suggests that climate indicators such as ENSO and IOD may not behave or evolve as they have in the past.
The Southern Annular Mode (SAM) is neutral (as at 27 October) and is forecast to remain mostly neutral over the coming fortnight. The months of November and December are tending towards positive SAM.
The Madden–Julian Oscillation (MJO) is currently in the Western Pacific (as at 27 October). Most models suggest a moderately strong MJO pulse will continue to move eastwards and weaken slightly as it moves across the Western Pacific and towards the Americas over the coming fortnight.
ENSO, IOD, MJO and SAM are broad indicators of the expected climate and are just some of many factors in a complex system. The long-range forecast provides better guidance on local rainfall and temperature patterns.
