MELBOURNE, Australia – Sea surface temperatures (SSTs) in the central Pacific Ocean are ENSO-neutral, but have been cooling since December 2023, reports the Bureau of Meteorology of the Australian Government in its latest update. This surface cooling is being sustained by deep waters surfacing in the central and eastern Pacific.
Since June, the rate and extent of cooling both at the surface and at depth have slowed. Atmospheric patterns, including cloud and surface pressure, are currently ENSO-neutral.
ENSO is likely to remain neutral until at least early spring. Four of 7 climate models suggest the possibility of SSTs reaching the La Niña threshold (below −0.8 °C) by October. The remaining 3 models maintain ENSO-neutral throughout the forecast period. Compared with earlier forecasts, the potential for La Niña development is now later in spring.
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 either ENSO remaining neutral or La Niña developing during the remainder of 2024.
The Indian Ocean Dipole (IOD) is currently neutral. The latest model outlooks indicate that the IOD is likely to remain neutral until at least the end of winter. Three of 5 climate models suggest that during spring, negative IOD development is likely, while 2 maintain a neutral state of the IOD.
Global SSTs have been the warmest on record for each month between April 2023 and June 2024. July 2024 SSTs are comparable with 2023 but are much warmer than for any other July on record. The current global pattern of warmth differs to historical patterns of SSTs associated with ENSO and IOD.
This means future predictions based on SSTs during past ENSO or IOD 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 neutral (as at 20 July). The index is forecast to remain neutral for the coming fortnight, beyond which predictability of the SAM is typically low.
The Madden–Julian Oscillation (MJO) is currently weak or indiscernible (as at 20 July). Most models forecast it to remain weak for the coming fortnight. A weak MJO has little impact on Australian rainfall.
