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

SSTs for February 2023 were close to average across much of the tropical Pacific Ocean. Weak cool anomalies existed from around 165°E to around 120°W, being less than 1 °C cooler than average. Warm anomalies up to 2 °C warmer than average were present east of 110°W, increasing to up to 3 °C warmer than average close to the Peruvian coast.

Compared to January, cool SST anomalies in the tropical Pacific have weakened while warm SST anomalies have strengthened in the far east of the basin.

Warm anomalies up to 2 degrees above average were observed in a band across the South Pacific stretching from the South American coast around 40°S towards the Coral Sea, while weaker warm anomalies were present over northern areas of the Maritime Continent. Warm SST anomalies also continued to the west and south-east of Australia, especially around Tasmania and in waters close to New Zealand.

For the week ending 12 March 2023, sea surface temperatures (SST) were close to average across much of the equatorial Pacific Ocean. Compared to two weeks ago, warm anomalies east of 130°W have increased in strength and spatial extent, reaching more than 1 °C warmer than average in some areas. The small area of weak cool anomalies which was present in the central equatorial Pacific two weeks ago has dissipated.

Weak warm SST anomalies continue across parts of the north of Maritime Continent and in areas to the north-east of Australia. Warm SST anomalies continue to the south-west and south-east of Australia, especially around Tasmania and in waters close to New Zealand.

The latest values of the three NINO indices for the week ending 12 March 2023 were: NINO3 +0.4 °C, NINO3.4 0.0 °C, and NINO4 −0.1 °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 12 March 2023 was +5.4, while the 90-day SOI value was +13.2. The 30-day SOI has decreased over the past fortnight, and is now within neutral values for the first time since November 2022.

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 12 March 2023 were close to average across the tropical Pacific Ocean.

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) is currently very strong over the eastern Pacific Ocean but is forecast to move into the Atlantic Ocean in the coming fortnight. This may bring drier conditions to Australia for the latter half of March.

The Indian Ocean Dipole (IOD) is currently neutral. The IOD typically has little influence on Australian climate while the monsoon trough is in the southern hemisphere (December to April). The IOD index value for the week ending 12 March 2023 was +0.19 °C; within neutral bounds (between −0.40 °C and +0.40 °C).

Sea surface temperatures (SSTs) are generally close to average along the equator of the Indian Ocean. A small area of cool SST anomalies exists off the African coastline while warm SST anomalies are present off the west coast of Australia and over much of the south of the basin.

Most international climate models surveyed by the Bureau anticipate neutral values of the IOD index will continue through the southern hemisphere autumn, though one model forecasts the positive IOD threshold will be exceeded in April. While models suggest positive IOD values may emerge during winter, IOD forecasts made at this time of the year have very low accuracy when forecasting through the autumn.

Cloudiness near the Date Line has been mostly below average (i.e. positive outgoing longwave radiation (OLR) anomalies) since June 2021. Despite OLR values returning to near average late in February, OLR anomalies have been positive for the past fortnight after dipping below zero in late February.

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

The four-month sequence of equatorial Pacific sub-surface temperature anomalies (to 28 February 2023) shows weak cool anomalies across the top 150 m of the central to eastern equatorial Pacific. Warm anomalies are in place between around 50 and 300 m depth in the western to central equatorial Pacific (west of 160°W). Anomalies reached more than 3 °C warmer than average across much of this region.

Compared to previous months, cool anomalies have decreased in strength steadily over the summer, while warm anomalies have remained consistent during February when compared to those for January.

For the five days ending 12 March 2023, sub-surface temperatures were significantly warmer than average across the western to central equatorial Pacific between about 100 m depth and 250 m depth, reaching more than 4 °C warmer than average west of the Date Line. Weak cool anomalies were present between 140°W and 120°W at depths between 100 m and 150m depth.

Compared to two weeks ago, warm anomalies in the western Pacific sub-surface have increased in strength and extent.

La Niña has ended in the tropical Pacific Ocean. The El Niño–Southern Oscillation (ENSO) is now neutral (neither La Niña nor El Niño) with oceanic and atmospheric indicators having returned to neutral ENSO levels.

International climate models suggest neutral ENSO conditions are likely to persist through the southern autumn. However, there are some signs that El Niño could form later in the year. Hence the Bureau has issued an El Niño WATCH. This means there is around a 50% chance of an El Niño in 2023.

The Madden–Julian Oscillation (MJO) is currently very strong over the Pacific Ocean but is forecast to move into the Atlantic Ocean in the coming fortnight. This may bring drier conditions to Australia for the latter half of March.

The Southern Annular Mode (SAM) index is currently strongly negative but is expected to return to neutral values over the coming week.

Warmer than average sea surface temperatures persist around south-east Australia, New Zealand and the west coast of Australia, but close to average temperatures prevail around northern Australia.

The Indian Ocean Dipole (IOD) is neutral – the IOD typically has little influence on Australian climate while the monsoon trough is in the southern hemisphere (typically December to April). Forecasts for the IOD made at this time of the year have low accuracy beyond April.

Climate change continues to influence Australian and global climates. Australia's climate has warmed by around 1.47 °C over 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. Southern Australia has seen a reduction of 10 to 20% in cool season (April–October) rainfall in recent decades.

The Southern Annular Mode (SAM) index is currently the strongest negative value since June 2022, but is expected to return to neutral values over the coming week.

Neutral SAM has little influence on the rainfall and temperature outlook for Australia.

The 2022–23 La Niña has ended, having been declared in September 2022. Oceanic and atmospheric indicators have returned to ENSO-neutral (neither El Niño nor La Niña) values.

All but one of the seven international climate models surveyed by the Bureau anticipate central Pacific sea-surface temperatures will remain ENSO-neutral through the southern hemisphere autumn; one model exceeds El Niño thresholds in May. While several models suggest El Niño may develop later in 2023, model accuracy when forecasting through autumn is lower than at other times of the year, and ENSO outlooks that extend past autumn should be viewed with some caution.

The Bureau's ENSO Outlook has been moved to El Niño WATCH. An El Niño WATCH means that there is around a 50% chance that an El Niño will develop. This is about twice the normal likelihood of an El Niño forming in any year. An El Niño WATCH is not a guarantee that El Niño will occur, rather it is an indication that some of the typical precursors of an event are currently observed.