Climate Driver Update history
Climate drivers in the Pacific, Indian and Southern oceans and the Tropics

In the tropical Pacific Ocean, September sea surface temperatures (SSTs) were:

• up to 1.2 °C warmer than average in the far western tropical and far eastern equatorial Pacific Ocean
• up to 1.2 °C cooler than average in the central and eastern equatorial Pacific and along parts of the South American coast.

In Australian coastal waters, September SSTs were:

• up to 2 °C warmer than average in waters surrounding most of Australia, reaching up to 3 °C warmer than average off the north-west coast.

Around the Maritime Continent, September SSTs were:

• up to 2 °C warmer than average.

The Bureau's long-range forecast for November 2024 to January 2025 indicates SSTs are likely to be:

• up to 1.2 °C warmer than average in the far western Pacific (west of 170°E)
• up to 0.8 °C cooler than average in the eastern equatorial Pacific (between 150°W and 100°W)
• up to 1.2 °C warmer than average across most of Australian coastal waters, and reaching up to 2 °C warmer in the north-west and south-east
• up to 1.2 °C warmer than average across the Maritime Continent.

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.

For the week ending 13 October 2024, sea surface temperatures (SSTs) were:

• 0.8–2 °C warmer than the 1991–2020 average in the far western and parts of the far eastern equatorial Pacific
• 0.8–2 °C cooler than average in the central equatorial Pacific
• warmer than average across much of the north Pacific, with much of the region surrounding and to the east of Japan more than 3–4 °C warmer than average
• 0.8–2 °C warmer than average around the north-west of Australia's coastline and parts of the Tasman and Coral seas
• 0.4–1.2 °C warmer than average across most of the Maritime Continent.

The Niño indices for the week ending 13 October 2024 are: Niño3, −0.1 °C; Niño3.4, −0.5 °C; and Niño4, +0.04 °C. The Niño3.4 index reflects historically neutral ENSO conditions.

• The 30–, 60– and 90-day Southern Oscillation Index (SOI) for the period ending 13 October were +1.8, +5.0 and +0.9 respectively.
• The SOI values reflect ENSO-neutral conditions.
• Sustained positive values of the SOI above +7 typically indicate La Niña while sustained negative values below −7 typically indicate El Niño. Values between +7 and −7 generally indicate neutral conditions.

• Trade wind strength for the 5 days ending 13 October was near to slightly above average across the western and central tropical Pacific.
• Monthly averaged trade winds have been stronger than average across the equatorial Pacific since July.
• During La Niña events, there is typically a sustained strengthening of trade winds across much of the tropical Pacific, while during El Niño there is a sustained weakening, or even reversal, of trade winds.

• The Madden–Julian Oscillation (MJO) is currently indiscernible (as of 13 October).
• Most models suggest a moderately strong MJO pulse will develop over the Maritime Continent in the coming days and move eastwards in the coming week.

Current state

• The Indian Ocean Dipole (IOD) is neutral. The IOD index for the week ending 13 October was −0.58 °C.
• While the IOD index is below the negative IOD threshold, the IOD is currently neutral.
• Sea surface temperatures (SSTs) for the week ending 13 October 2024 were 0.8–2 °C warmer than the 1991–2020 average across much of the central and eastern Indian Ocean but 0.4–1.2 °C cooler than average in parts of the western Indian Ocean.
• Closer to Australia, SSTs were up to 2 °C warmer than average for waters surrounding northern WA.

Forecast

• Most climate models indicate the IOD is likely to remain neutral, but weakly negative, for the rest of the year.
• All models indicate the IOD index will meet or exceed negative IOD thresholds in November, though this would not see the index sustained for a sufficient period to be considered a negative IOD event.
• IOD forecast skill has historically been low at this time of year for forecasts beyond two months ahead.

• Cloudiness near the equatorial International Date Line is currently below average as of 12 October.
• Cloudiness has been below average since early September.
• Prior to September, cloudiness has fluctuated around average levels for most of the year.
• Equatorial cloudiness near the International Date Line typically increases during El Niño (below average outgoing longwave radiation - OLR) and decreases during La Niña (above average OLR).

The equatorial Pacific sub-surface temperature anomalies for the 30 days ending 10 October 2024 show:

• cooler than average waters in the eastern half of the equatorial Pacific down to about 200 m depth; cooler waters peak around 75 to 100 m depth in the central Pacific where they are more than 5 °C cooler than average.
• warmer than average waters in the western half of the equatorial Pacific down to about 200 m depth, increasing to 300 m depth in the far west. Waters are 2 to 3 °C warmer than average in a few small pockets around 125 m depth.

For the 5 days ending 13 October 2024, the analysis shows:

• sub-surface temperatures around 1 °C cooler than average in the central equatorial Pacific (between 125 m and 200 m depth) and in the eastern equatorial Pacific (between 50 m and 100 m depth).
• sub-surface temperature anomalies more than 3 °C warmer than average in the shallow eastern equatorial sub-surface (above 50 m depth).

The El Niño–Southern Oscillation (ENSO) is neutral, with both sea surface temperatures (SSTs) in the central equatorial Pacific Ocean and atmospheric patterns at ENSO-neutral levels. Atmospheric indices, such as those related to pattens of surface pressure, cloud and trade winds, are broadly consistent with an ENSO-neutral state. Although some have displayed La Niña-like signals over the past several weeks, these signals have not been consistent.

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, 4 also suggest SSTs will remain within the ENSO-neutral thresholds. Only one model suggests SSTs in the tropical Pacific are likely to exceed the La Niña threshold (below −0.8 °C) throughout November to January, with another forecasting SSTs to briefly exceed the threshold, but only during December and January. The chance of a La Niña event developing in the coming months has decreased compared to recent outlooks. If a La Niña were to develop, it is forecast to be relatively weak (in terms of the strength of the SST anomaly) and short-lived, with all models forecasting neutral values in February.

The Indian Ocean Dipole (IOD) is currently neutral, despite the weekly IOD index value (−0.58 °C) dropping below the negative IOD threshold (−0.40 °C) in the week ending 13 October. All models indicate that the IOD is likely to remain neutral, but weakly negative, for the rest of the year. Forecasts indicate a sustained period of negative values is unlikely, but due to fluctuations in the tropical Indian Ocean SST patterns, the IOD index may drop, briefly, below the negative IOD threshold.

Global SSTs remain at near-record levels, with temperatures since July being just short of the record temperatures observed during 2023, yet well 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 necessarily behave or evolve as they have in the past.

The Southern Annular Mode (SAM) is neutral (as at 13 October) and forecast to remain neutral over the coming fortnight.

The Madden–Julian Oscillation (MJO) is currently indiscernible (as at 13 October). Most models suggest a moderately strong MJO pulse will emerge in the Maritime Continent over the coming days, and then move eastward in the coming week.

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.

• The Southern Annular Mode (SAM) is neutral (as of 13 October) and forecast to remain neutral in the coming fortnight.
• Predictability of the SAM beyond two weeks is typically low.

• ENSO is currently neutral.
• The Bureau's model suggests SSTs are likely to remain within the ENSO-neutral range (−0.8 °C to +0.8 °C) throughout the forecast period.
• Of the 6 other climate models surveyed, only one suggests SSTs in the tropical Pacific are likely to exceed the La Niña threshold (below −0.8 °C) throughout November to January, and one forecasting SSTs below the threshold but for only December and January.
• Should a La Niña develop in the coming months, it is forecast to be relatively weak (in terms of the magnitude of the SST anomaly) and short-lived, with all models indicating neutral-ENSO by February 2025.
• The likelihood of a La Niña developing in the coming months has decreased compared to recent updates.
• ENSO forecast skill is high at this time of year for up to 4 months ahead.