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

SSTs for June 2023 were warmer than average over the entirety of the tropical Pacific Ocean and much of areas south of 10° S. Warm anomalies more than 1.2 °C warmer than average were present over parts of these regions, increasing to more than 3 °C warmer than average off small, isolated parts of the South American coast.

Compared to May, warm anomalies in the east equatorial tropical Pacific Ocean have extended westwards. Parts of the basin have cooled marginally in the southern central and eastern parts of the South Pacific Ocean. A band of warm anomalies in the south-west Pacific persists from the south-east of Papua New Guinea south-eastwards to around New Caledonia, Vanuatu, Fiji and the east of New Zealand.

Warm SST anomalies also continued in the southern Tasman Sea, between south-east Australia and New Zealand, as well as to the south-west of Western Australia. Cool anomalies off the east coast of New South Wales decreased in strength and spatial coverage during May with a new small cool anomaly developing of the south of WA.

Globally, the April and May 2023 SSTs were the warmest on record for their respective months. In the ERSSTv5 dataset, the global area-average SST for April was 0.69 °C above the 1961-1990 average, average, exceeding the previous April record of 0.67 °C in 2019. Global SST for May was 0.70 °C above average (previous May record was 0.63 °C in 2020).

For the week ending 2 July 2023, sea surface temperatures (SSTs) were warmer than average across almost all of the equatorial region of the tropical Pacific Ocean. Anomalies were more than 2 °C over parts of the eastern Pacific Ocean, increasing to more than 4 °C warmer than average in isolated areas off the South American coast. Compared to two weeks ago, warm anomalies in the central and eastern tropical Pacific have remained at similar in strength and spatial extent. Warm anomalies more than 0.8 ° C warmer than average persists in the south-west Pacific from the south-east of Papua New Guinea extending south-eastwards to the east of New Zealand, decreasing marginally in spatial coverage over the last fortnight.

Closer to Australia, the Coral Sea has seen anomalously warm SSTs increase slightly in strength over the past two weeks, with anomalies more than 1.2 ° C warmer than average across much of the region. Warm SST anomalies persist in the southern Tasman Sea, from south-east Australia to around New Zealand, and near south-west Australia. The cold SST anomalies around the western and southern Australian coastline and off the NSW coast have increased in strength and spatial coverage in the last fortnight.

The latest values of the three NINO indices for the week ending 2 July 2023 were: NINO3 +1.49 °C, NINO3.4 +0.94 °C and NINO4 +0.63 °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-day Southern Oscillation Index (SOI) for the period ending 2 July 2023 was +1.1, returning to the neutral range over the past fortnight. Values for the 60-day SOI and the 90-day SOI were −8.6 and −5.5 respectively. Both the 30-day and 90-day SOI have shown a steady decrease in magnitude over the past month.

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

Trade winds for the 5 days ending 2 July 2023 were close to average over most of the tropical Pacific.

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 weak or indiscernible, with most climate models indicating the pulse will remain weak in the coming weeks. The MJO has little influence on Australian rainfall at this time of the year.

The Indian Ocean Dipole (IOD) is currently neutral. The IOD index for the week ending 2 July 2023 was −0.21 °C, which is within neutral bounds (between −0.40 °C and +0.40 °C).

Weekly sea surface temperatures (SSTs) for the period ending 2 July are above average across large areas of the central and western tropical Indian Ocean, decreasing in strength and spatial coverage in the last fortnight. Off the Horn of Africa, a small area of cool anomalies has also recently appeared. Warm anomalies continue to exist over much of the southern half of the basin, and to the south-west of Australia.

Closer to Australia, SSTs are close to average south of the Maritime Continent and cooler than average SST anomalies have formed around the western and southern coasts of the mainland.

All international climate models surveyed by the Bureau suggest a positive IOD event may develop in coming months. A positive IOD can supress winter–spring rainfall over much of central and south-east Australia, and if combined with El Niño, the drying effect is typically stronger and more widespread across Australia. Long-range forecasts of the IOD should be viewed with caution beyond August.

Cloudiness near the Date Line has recently been above average (i.e. negative outgoing longwave radiation (OLR) anomalies) but has returned to average where it has hovered since late April 2023. For a brief period last week, the OLR anomaly was the most negative it has been since the February 2020.

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

The four-month sequence of equatorial Pacific sub-surface temperature anomalies (to 30 June 2023) shows warm anomalies were present for most of the top 175 m of the equatorial Pacific band. Anomalies reached more than 3 °C warmer than average across much of this region.

June has seen warm anomalies continue to be present across the equatorial sub-surface and have strengthened in the eastern Pacific.

For the five days ending 2 July 2023, sub-surface temperatures were warmer than average across the equatorial Pacific, at depths between about 25 to 150 m in the western and central Pacific, and between the surface to 125 m depth in the eastern Pacific. Anomalies were more than 1 °C warmer than average across the basin, increasing to more than 3 °C in the central Pacific and 6 °C in the far east.

Compared to two weeks ago, warm anomalies have decreased marginally in strength in the west Pacific, while increasing slightly in the east.

The ENSO Outlook remains at El Niño Alert. When El Niño Alert criteria have been met in the past, an El Niño event has developed around 70% of the time.

Central and eastern Pacific sea surface temperatures (SSTs) are exceeding El Niño thresholds. Models indicate a high likelihood of further warming, with SSTs exceeding El Niño thresholds until at least the beginning of the southern hemisphere summer. In terms of atmospheric indicators, recent values of the Southern Oscillation Index (SOI) have risen back to neutral levels, with the 30-day SOI at +1.1 for the 30 days ending 2 July. The 90-day SOI remains close to, but just shy of, El Niño levels. Sustained changes in wind, cloud and broad-scale pressure patterns towards El Niño-like patterns have not yet been observed. This means the Pacific Ocean and atmosphere have yet to become fully coupled, as occurs during El Niño events. El Niño typically suppresses winter–spring rainfall in eastern Australia.

The current status of the ENSO Outlook does not change the long-range forecast of warmer and drier conditions across much of Australia for August to October. The Bureau's climate model takes into account all influences from the oceans and atmosphere when generating its long-range forecasts.

The Indian Ocean Dipole (IOD) is currently neutral. All models suggest a positive IOD is likely to develop in the coming months. A positive IOD typically supresses winter and spring rainfall over much of Australia, and if it coincides with El Niño, it can exacerbate El Niño's drying effect.

The Madden–Julian Oscillation (MJO) is currently weak or indiscernible, and is expected to remain weak in the coming fortnight. The MJO has little influence on Australian rainfall at this time of year.

The Southern Annular Mode (SAM) index is currently negative and is expected to remain negative for a week before returning to neutral values for at least the next two weeks. A negative SAM typically increases rainfall across parts of south-west and south-east Australia, while a neutral SAM has little influence on Australian climate.

Climate change continues to influence Australian and global climates. Global SSTs were the warmest on record for the months of April and May. The Australian continent has warmed by around 1.47 °C over the period 1910 to 2021. There has also been a trend towards a greater proportion of rainfall from high intensity, short duration rainfall events, especially across northern Australia. Southern Australia has seen a reduction, by 10 to 20%, in cool season (April to October) rainfall in recent decades. This is due to a combination of natural variability on decadal timescales and changes in large-scale circulation caused by an increase in greenhouse gas emissions.

The Southern Annular Mode (SAM) index is currently negative and is expected to remain negative for a week before returning to neutral values for at least the next two weeks. A neutral SAM has little influence on Australian climate.

Central and eastern Pacific sea surface temperatures (SSTs) currently exceed El Niño thresholds. International climate models suggest further warming of the central and eastern tropical Pacific Ocean is likely. All surveyed models indicate SSTs will remain above El Niño thresholds at least into the beginning of the southern hemisphere summer. If the atmosphere responds to this warming, an El Niño event would be expected to develop.

El Niño typically suppresses winter–spring rainfall in eastern Australia.