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

SSTs for December 2022 were cooler than average across the central and eastern tropical Pacific Ocean, extending from around 170°E to the South American coastline and across an area south of the equator to 20°S in the east of the basin.

Warm anomalies, up to 2 °C above the 1961–1990 average, were observed across waters to the north-east of Australia, particularly in the Coral Sea.

Weak warm anomalies have appeared to the west of Australia while cool anomalies have formed off the eastern coast of Australia, southwards of the Gold Coast.

Warm anomalies extend into the mid-latitudes in the southern Pacific and across the mid- to high latitudes in the north—a pattern characteristic of well-developed La Niña.

Cool anomalies for December were reduced in strength compared to those in November, especially just south of the equator. Warm anomalies to the north-east and south-east of Australia have also reduced in strength.

For the week ending 1 January 2023, sea surface temperatures (SST) were cooler than average across the central and eastern tropical Pacific Ocean (from the coast of South America to 170°E), consistent with a La Niña pattern. Cool SST anomalies are strongest in the eastern Pacific just to the south of the equator.

Warm SST anomalies continue in the far west of the Pacific, with generally small anomalies over the Maritime Continent, and larger anomalies to the north-east of Australia.

Compared to two weeks ago, cool SST anomalies in the eastern equatorial Pacific have weakened. The strength of warm anomalies has decreased over the Coral Sea (to the north-east of Australia), especially off the Queensland coast.

The latest values of the three NINO indices for the week ending 1 January 2023 were: NINO3 −0.5 °C, NINO3.4 −0.6 °C, and NINO4 −0.5 °C.

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

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 15 January 2023 was +20.9 while the 90-day SOI value was +13.1. Both have remained relatively similar over the last fortnight.

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 winds for the 5 days ending 15 January 2023 were stronger than average in the western and central tropical Pacific Ocean, westwards of 160°W. Elsewhere, trade wind strength was close to average.

During La Niña there is 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) has been weak since early January, but most models expect a strengthening pulse to develop over tropical Africa or the western Indian Ocean in the coming days, tracking further east towards the eastern Indian Ocean in the coming fortnight. This may lead to a period of suppressed rainfall across northern Australia, commencing in about a week, after the current weather-generating systems over Australia's north-east dissipate.

The Indian Ocean Dipole (IOD) is currently neutral and has little influence on Australian climate while the monsoon trough is in the southern hemisphere (typically December to April). The IOD index value for the week ending 15 January 2023 was +0.01 °C; within neutral bounds (between −0.4 °C and +0.4 °C).

Sea surface temperatures (SSTs) are generally close to average across most of the tropical Indian Ocean basin, although a small region of cool anomalies are present off the Kimberley and Pilbara coasts of Western Australia and in parts of the Maritime Continent.

All five international climate models surveyed by the Bureau anticipate neutral values of the IOD index will continue through summer and into the southern hemisphere autumn.

The four-month sequence of equatorial Pacific sub-surface temperature anomalies (to 1 January 2023) shows cool anomalies from the surface to around 150 m depth in the eastern half of the equatorial Pacific. Anomalies reached more than 2 °C cooler than average across much of the region east of 115°W to around 100m depth.

Warm anomalies persist between around 100 and 250 m depth west of the International Date Line. Anomalies reached more than 2 °C warmer than average across much of this region.

Compared to November, warm anomalies in December have increased in strength while cool anomalies have decreased in strength.

For the five days ending 15 January 2023, sub-surface temperatures were warmer than average across the equatorial Pacific, reaching more than 4 °C warmer than average around 150 to 200 m depth, west of the International Date Line. A small area of cooler than average temperatures exist in the eastern equatorial Pacific around 75 to 150 m depth east of 150°W. These are weaker than those in the western equatorial Pacific, reaching around 2 °C cooler than average.

Compared to two weeks ago, western Pacific sub-surface warm anomalies have strengthened though weak cool sub-surface anomalies in the eastern Pacific have reappeared.

La Niña continues in the tropical Pacific, but has weakened from its peak in spring 2022. Though ocean temperatures have warmed in recent weeks, atmospheric indicators are largely unchanged and remain at La Niña levels. La Niña typically increases the chance of above average rainfall for northern and eastern Australia during summer.

Long-range forecasts suggest that tropical Pacific Ocean temperatures will continue to warm and be at ENSO-neutral levels (neither La Niña nor El Niño) during February, with a change in atmospheric patterns towards neutral levels likely to follow. As accuracy is generally lower for long-range forecasts made at this time of year, ENSO outlooks that extend past autumn should be viewed with caution.

The Indian Ocean Dipole (IOD) is neutral and has little influence on Australian climate while the monsoon trough is in the southern hemisphere (typically December to April).

The Southern Annular Mode (SAM) is strongly positive and is likely to be positive into late-January. During summer, when SAM is positive there is typically an increased chance of above average rainfall for eastern New South Wales, eastern Victoria and north-east Tasmania and below average rainfall for western Tasmania.

The Madden–Julian Oscillation (MJO) has been weak since early January, but most models expect a strengthening pulse to develop over tropical Africa or the western Indian Ocean in the coming days, tracking further east towards the eastern Indian Ocean in the coming fortnight. This may lead to a period of suppressed rainfall across northern Australia, commencing in about a week, after the current weather-generating systems over Australia's north-east dissipate.

Sea surface temperatures remain warmer than average in the western tropical Pacific, northern Maritime Continent, and to the south and south-east of Australia from the Eyre Peninsula to waters east of New Zealand. Warmer Australian waters, especially in the tropics, can result in greater evaporation, humidity, cloudiness, and rainfall.

Climate change continues to influence Australian and global climates. Australia's climate has warmed by around 1.47 °C in the period 1910–2021. There has also been a trend towards a greater proportion of rainfall from high intensity short duration rainfall events, especially across northern Australia.

The Southern Annular Mode (SAM) index has been strongly positive for the past fortnight and is likely to remain positive until at late-January before becoming weakly positive to neutral. The positive phase of the SAM is being boosted by La Niña and a strong stratospheric polar vortex over Antarctica.

In summer months, a positive SAM increases the chance of above average rainfall for parts of north-east Tasmania, eastern Victoria, eastern New South Wales and south-eastern Queensland, and increases the chance of below average rainfall for western Tasmania.

A La Niña is under way in the tropical Pacific. While Pacific Ocean temperatures have warmed in recent weeks, atmospheric indicators have yet to respond. The Bureau's ENSO Outlook continues at LA NIÑA.

All of the seven international climate models surveyed by the Bureau anticipate central Pacific sea-surface temperatures will be ENSO-neutral during February.

ENSO events typically peak in late (southern hemisphere) summer and decay during the autumn;

La Niña events increase the chance of above-average rainfall for northern and eastern Australia during summer. Even as La Niña weakens, it can continue to influence global weather and climate.

ENSO is not the only driver influencing Australia's climate. Other factors such as warmer than average SSTs to Australia's north-east are also contributing to current outlooks. The Bureau's long-range forecast indicates some parts of eastern and northern Australia are likely to be wetter than average over the next three months.