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

Sea surface temperatures (SSTs) for October 2023 were warmer than average over almost all of the equatorial Pacific Ocean. Over much of the Pacific, between 10°S and 10°N, SST anomalies were more than 0.8 °C warmer than the long-term average (1961–1990), increasing to up to 3 °C warmer than the long-term average in the parts of western tropical Pacific and up to 4 °C warmer than average in parts of the eastern tropical Pacific. Much of the central southern Pacific was also warmer than average for October.

The extent of warm anomalies in the central tropical Pacific were slightly higher than in September.

Warm SST anomalies also continued in the western Tasman Sea, including off most of the eastern coast of Australia, but weakened in eastern Tasman Sea. Warm anomalies to the west of Australia increased in extent, with waters warmer than 2 °C above average off parts of the north-west coast of Western Australia.

Globally, SSTs for April to October 2023 were warmest on record (since 1900) for their respective months. In the ERSSTv5 dataset, August 2023 SSTs were also the warmest globally for any month since observational records began in 1854, with September 2023 being the second-warmest.

For the week ending 19 November 2023, sea surface temperatures (SSTs) were warmer than average across most of the equatorial region of the tropical Pacific Ocean. Anomalies were more than 1.2 °C warmer than average east of 170°E, increasing to more than 2 °C warmer than average in some areas of the central and eastern tropical Pacific. Compared to last fortnight, warm anomalies have generally decreased except around 170°E where it has increased.

Closer to Australia, warm anomalies up to 3 °C above average persist off the coast of south-east Australia, extending into the southern Tasman Sea. There were also warm SST anomalies off the north-west and south-west coasts of Australia, mostly up to about 1.2 °C above average. Compared to last fortnight, warm anomalies to the south-east of Australia have increased in magnitude, but to the west of Australia, they have decreased. Cool anomalies up to 1.2 °C below average have developed in the western Coral Sea.

The latest values of the three NINO indices for the week ending 19 November 2023 were: NINO3, +1.80 °C; NINO3.4, +1.78 °C; and NINO4, +1.54 °C.

Persistent NINO3 or NINO3.4 values warmer than +0.8 °C are typical of El Niño, while persistent values cooler than –0.8 °C typically indicate La Niña.

The 30–, 60– and 90-day Southern Oscillation Index (SOI) values for the period ending 19 November 2023 were −7.8, −8.2 and −11.1, respectively.

Sustained negative values of SOI below −7 typically indicate El Niño, while sustained positive values above +7 typically indicate La Niña.

Trade winds for the 5 days ending 19 November 2023 were weaker than average over most of the equatorial Pacific. Over parts of the western equatorial Pacific, there was a reversal in the mean direction of winds from the typical easterly to a westerly. 

Trade winds for October 2023 have been slightly weaker to weaker than average across the equatorial Pacific. Trade winds have been weaker than average over the central equatorial Pacific for most of the last three months. 

During El Niño, there is a sustained weakening, or even reversal, of trade winds across much of the tropical Pacific, while during La Niña, there is a sustained strengthening of trade winds.

The Madden–Julian Oscillation (MJO) is currently over the Western Hemisphere and Africa. International climate models suggest it will move to the Indian Ocean by the end of November. When the MJO is in the western Indian Ocean, it typically has a drying influence on northern and eastern Australia.

The positive Indian Ocean Dipole (IOD) event continues. It is currently tracking as a strong event. The IOD index is +1.49 °C for the week ending 19 November 2023. The weekly IOD index values for this event have been the second-highest since records for the Bureau SST dataset began in 2001, with the highest values occurring in the strong positive IOD event of 2019. The highest weekly IOD index for this event so far was +1.92 °C for the week ending 15 October. 

Sea surface temperatures (SSTs) for the week ending 19 November show warmer than average waters in much of the western half of the tropical Indian Ocean, as well as for waters south of 15°S. Conversely, the eastern pole of the IOD was cooler than average, with an area of cooler waters extending off the coast of Java, Indonesia. This shows a clear gradient between the western and eastern tropical Indian Ocean that is typical of a positive IOD. Compared to last fortnight, the strength and extent of the cooling in the eastern pole has reduced while there has been a slight increase in the strength of the anomalous warmth in the western pole. 

The IOD tends to break down as the monsoon trough moves south into the southern hemisphere, usually around the end of the southern hemisphere spring. Given the current strength of the positive IOD event, the break down this year is likely to be slightly later than usual. Additionally, during El Niño, the onset of the North Australian Monsoon tends to be delayed. All international climate models surveyed by the Bureau suggest the positive IOD event is likely to ease in December. 

A positive IOD typically leads to reduced spring rainfall for central and south-east Australia.  If the positive IOD persists into December, these impacts tend to persist as well, though typically to a lesser degree.

Outgoing Longwave Radiation (OLR) around the equatorial Date Line is currently above average (indicating decreased cloudiness). However, OLR has been mostly below average since mid-September 2023, indicating above average cloudiness. 

Equatorial cloudiness near the Date Line typically increases during El Niño (negative OLR anomalies) and decreases during La Niña (positive OLR anomalies).

The 4-month sequence of equatorial Pacific sub-surface temperature anomalies (to 31 October 2023) shows warm anomalies across most of the top 100 m of the equatorial Pacific band, with the exception of the far west. Anomalies increase in magnitude eastwards across the equatorial Pacific band, with the far west close to average, the central Pacific up to 2.5 °C warmer than average, and the eastern Pacific more than 2.5 °C warmer than average.

The past 4 months have seen sub-surface heat shift towards the surface. Compared to July 2023, warm sub-surface anomalies in the eastern Pacific have decreased, but near the Date Line, in the top 100 m, they have increased. West of the Date Line, temperatures have decreased such that most of the water column is now close to average. Below average temperatures have emerged between 100 m and 300 m depth west of 170°E.

For the 5 days ending 19 November 2023, sub-surface temperatures were warmer than average across the upper levels of the equatorial Pacific between the surface to around 100 m depth in the eastern Pacific, between the surface to around 200 m depth in the central Pacific, and between the surface to around 150 m depth in the far western Pacific. Much of this region was more than 2 °C warmer than average, with anomalies more than 5°C warmer than average between 135°W and 110°W.

Compared to last fortnight, the extent of warm anomalies in the eastern and western Pacific have increased. Slight weak cool anomalies continue to persist at depths around 200 m below the surface in areas west of the Date Line.

El Niño continues in the tropical Pacific. Warmer than average sea surface temperatures (SSTs) persist in the tropical Pacific, with warmer water beneath the surface to support further surface warming. In the atmosphere, cloud, wind and pressure patterns are consistent with El Niño conditions. Climate model forecasts indicate some further warming of the central to eastern Pacific is possible, with SSTs remaining above El Niño thresholds into the early southern hemisphere autumn 2024. The 2023 El Niño event is tracking around moderate strength.

The positive Indian Ocean Dipole (IOD) event continues and is currently tracking at strong levels. IOD events tend to break down as the monsoon trough moves south into the southern hemisphere, usually around the end of the southern hemisphere spring. Given the current strength of the positive IOD event, the break down this year is likely to be slightly later than usual. All international climate models surveyed by the Bureau suggest the positive IOD is likely to ease in December.

The Southern Annular Mode (SAM) index is neutral. Forecasts indicate it will remain neutral for the next fortnight. A neutral SAM has limited influence on Australian climate.

The Madden–Julian Oscillation (MJO) is currently over the Western Hemisphere and Africa. International climate models suggest it will move to the Indian Ocean by the end of November. When the MJO is in the western Indian Ocean, it typically has a drying influence on northern and eastern Australia.

Global warming continues to influence Australian and global climate. Global sea surface temperatures (SSTs) were highest on record for their respective months during April to October.

Australia's climate has warmed by 1.48 ± 0.23 °C since national records began in 1910. There has been an increase in extreme heat and fire weather associated with the warming. There has also been a trend towards a greater proportion of rainfall from high intensity, short duration rainfall events, especially across northern Australia.

The long-range forecast for Australia indicates December to February rainfall is likely to be below average across much of northern Queensland, the NT, Tasmania, southern and central SA, and north-west and western WA. Warmer days and nights are very likely almost nationwide. The Bureau's climate model includes all influences on Australian climate when generating its forecasts.

The Southern Annular Mode (SAM) index is neutral. Forecasts indicate it will remain neutral for the next fortnight. During spring, a neutral SAM is associated with typical climate conditions for Australia.

International climate models suggest some further warming of the central to eastern tropical Pacific Ocean is possible. All surveyed models indicate SSTs will remain above El Niño thresholds into early southern hemisphere autumn 2024. The 2023 El Niño event is tracking around moderate strength. 

Closer to Australia, Bureau long-range forecasts indicate warmer than average SSTs (up to around 2 °C warmer than average) off the coast of south-east Australia will likely continue through the southern hemisphere summer 2023–24. 

During spring, El Niño typically increases the chance of below average rainfall for eastern Australia and warmer than average days for the southern two-thirds of Australia. In summer, El Niño increases the likelihood of drier than average conditions for the north-east of Australia and warmer than average days across much of the eastern half of the country.