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

SSTs for June 2022 were generally close to average close to the equator across the Pacific, but SSTs were slightly cooler than average over much of the tropical central and eastern Pacific south of the equator, and in some scattered areas north of the equator. Cool anomalies were strongest close to South America. Warm SST anomalies were present over much of the Maritime Continent.

Compared to May, cool anomalies have weakened, while warm anomalies around northern Australia and to Australia's north-east have strengthened.

Values of the three key NINO indices for June 2022 were: NINO3 −0.3 °C, NINO3.4 −0.4 °C, and NINO4 −0.3 °C.

Data for the full month of July is not yet available.

For the week ending 31 July 2022, sea surface temperatures (SST) in the tropical Pacific Ocean were slightly cooler than average along with equator between 160°E and 140°W. Elsewhere, Pacific equatorial SSTs are close to average with small pockets of weak warm anomalies in parts of the eastern equatorial Pacific. Cool SST anomalies are persisting over much of the tropical central and eastern Pacific south of the equator.

Warm SST anomalies continue over the Maritime Continent and around much of Australia.

The latest values of the three NINO indices for the week ending 31 July 2022 were: NINO3 0.0 °C, NINO3.4 −0.4 °C, and NINO4 −0.6 °C.

These numbers are based on data available at the time of publication. Some data that is used to create the global ocean maps was not available within the usual timeframe. This is due to an external issue, outside of the Bureau's control.

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 31 July 2022 was +8.7. The 90-day SOI value was +15.2.

The 30-day SOI has fallen over the past fortnight to values just above the La Niña threshold. Much of the persistent positive SOI signal is due to high pressures over Tahiti; pressures near Darwin are near normal for the past 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 31 July 2022 were stronger than average over most of the western half of the tropical Pacific. Anomalies were close to average over the eastern tropical Pacific.

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

The Madden–Julian Oscillation (MJO) is currently weak, and is expected to remain so for the coming week before potentially re-strengthening in the Indian Ocean.

A negative Indian Ocean Dipole is under way with the latest Indian Ocean Dipole (IOD) index value for the week ending 31 July 2022 being −0.9 °C. This number, and the related IOD assessment, is based on data available at the time of publication. Some parts of the data set that is used to create the global ocean maps was not available within the usual timeframe. This is due to an external issue, outside of the Bureau's control.

The IOD index value has been continuously at or below the threshold (−0.4 °C) for the most recent eight weeks.

Cool anomalies are present close to the Horn of Africa in the north-west of the Indian Ocean basin, while weak warm SST anomalies continue across the east of the Indian Ocean between Indonesia and Australia. The establishment of a clear gradient in the temperature anomalies across the Indian Ocean is consistent with a negative Indian Ocean Dipole pattern.

All five international climate models surveyed by the Bureau anticipate a negative IOD is likely to persist through to November.

A negative IOD increases the chances of above average winter–spring rainfall for much of Australia. It also increases the chances of warmer days and nights for northern Australia.

Cloudiness near the Date Line had been consistently below average (i.e. positive outgoing longwave radiation, or OLR, anomalies) since June 2021. It continued to be below average through July 2022 with only a few periods of close to average anomalies since late May, most recently during the middle of July.

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 July 2022) shows a small area of weak cool anomalies has appeared in the central equatorial Pacific up to 200 m in depth, with weak warm anomalies persisting but decreasing in extent in the western and eastern tropical Pacific subsurface, as compared to June.

This breaks the month-on-month trends of warm anomalies increasing their eastward extent during autumn and into June.

For the five days ending 31 July 2022, sub-surface temperatures along the equator were mostly close to average. Temperatures were more than 2 degrees warmer than average between 50 m and 100 m depth in a region extending east of 120°W, and between 100 m and 150 m depth around the Date Line. Between a depth of 100 m and 150 m in a region between 160°W and 120°W, temperatures were more than 2 degrees cooler than average. Compared to two weeks ago, these regions of warm anomalies have decreased in strength while the region of cool anomalies has increased in strength.

A negative Indian Ocean Dipole (IOD) event is under way. The IOD index has been very close to or exceeded negative IOD thresholds (i.e., at or below −0.4 °C) over the past eight weeks. All climate model outlooks surveyed indicate that negative IOD conditions are likely to continue into late spring. A negative IOD event is associated with above average winter–spring rainfall for much of Australia.

The Bureau's ENSO Outlook remains at La Niña WATCH, meaning there is around a 50% chance (double the normal likelihood) of La Niña forming later in 2022. This is a result of current observations and model outlooks. La Niña events increase the chance of above average winter–spring rainfall across much of northern and eastern Australia

El Niño–Southern Oscillation (ENSO) ocean indicators are currently at neutral levels. However, some atmospheric indicators, such as the Southern Oscillation Index, continue to show a residual La Niña-like signal. Trade winds have also recently re-strengthened in the western Pacific (more La Niña-like).

Three of seven climate models surveyed by the Bureau suggest La Niña could return in early southern hemisphere spring, with a fourth in late spring. The remaining three models persist at neutral ENSO levels.

The Madden–Julian Oscillation (MJO) is currently weak. Most models suggest the MJO is likely to remain weak or indiscernible over the coming week. The means it is likely to exert little or no influence on global tropical weather.

The Southern Annular Mode (SAM) index is currently neutral, with neutral to weakly positive values forecast for the rest of August. Positive SAM has a drying influence for parts of south-west and south-east Australia, while neutral SAM has little influence on Australian rainfall.

Climate change continues to influence Australian and global climate. Australia's climate has warmed by around 1.47 °C for the 1910–2020 period. Southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.There has also been a trend towards a greater proportion of rainfall from high intensity short duration rainfall events, especially across northern Australia.

Please note: ENSO and IOD index values are based on data available at the time of publication. Some data that is used to create our global ocean maps was not available within the usual timeframe. This is due to an external issue, outside of the Bureau's control.

The Southern Annular Mode (SAM) index is currently neutral. Values in July were neutral to positive and are expected to be neutral to positive during August.

Neutral SAM has little influence on Australian rainfall, while positive SAM has a drying influence for parts of south-west and south-east Australia at this time of year.

The El Niño–Southern Oscillation is currently neutral. However, some models suggest that La Niña may re-form later in 2022 during the southern hemisphere spring.

Five of seven surveyed international climate models predict neutral but cooler than average temperatures in the central tropical Pacific to persist throughout the southern winter, while two show stronger cooling, reaching La Niña thresholds (−0.8 °C) by late winter. In October, four of the seven models indicate SSTs in the central equatorial Pacific Ocean will reach or exceed La Niña threshold values.

While back-to-back La Niña events are not uncommon, and have occurred in approximately half of all past events since 1900, three in a row is less common and has only occurred three times since 1900: 1954–57, 1973–76, and 1998–2001.

Despite the end of the 2021–22 La Niña, the Bureau's long-range climate outlook remains wetter than average for most of Australia, reflecting a range of climate drivers including a developing negative Indian Ocean Dipole, and warmer than average waters around Australia.