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

SSTs for July 2022 were slightly cooler than average along the equator between 160°E and 160°W, with SSTs generally close to average along the rest of the equator across the Pacific. SSTs were also slightly cooler than average over much of the tropical central and eastern Pacific south of the equator. As during June, cool anomalies were strongest close to South America. Warm SST anomalies were present over much of the Maritime Continent.

Compared to June, cool anomalies have strengthened in the central tropical Pacific, while warm anomalies around north-western Australia, the Top End, and Gulf of Carpentaria have strengthened.

Values of the three key NINO indices for July 2022 were: NINO3 −0.1 °C, NINO3.4 −0.4 °C, and NINO4 −0.6 °C.

For the week ending 14 August 2022, sea surface temperatures (SST) in the tropical Pacific Ocean were cooler than average along much of the equator between 160°E and 110°W. Compared to two weeks ago, cool anomalies have strengthened and increased in extent in the central equatorial Pacific. Cool SST anomalies persist to the south of the equator in much of the tropical central and eastern Pacific. A small area of warm anomalies remains in the eastern equatorial Pacific, between 110°W and the South American coastline.

Warm SST anomalies continue over the Maritime Continent and around much of Australia; mostly in the north, south-east, and south-west.

The latest values of the three NINO indices for the week ending 14 August 2022 were: NINO3 −0.2 °C, NINO3.4 −0.6 °C, and NINO4 −0.6 °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 14 August 2022 was +11.0. The 90-day SOI value was +13.9.

The 30-day SOI has risen slightly over 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 14 August 2022 were slightly stronger than average over much of the western half of the tropical Pacific. Trade wind 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, but may potentially re-strengthen over Africa or the Indian Ocean in the coming days. A weak or indiscernible MJO has little influence on Australian climate, while MJO over the Indian Ocean may bring warmer days to parts of western and south-eastern Australia at this time of year.

A negative Indian Ocean Dipole is underway. The latest Indian Ocean Dipole (IOD) index value, for the week ending 14 August2022, was −1.15 °C. The IOD index value has been continuously at or below the threshold (−0.4 °C) since mid-June.

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

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.

All five international climate models surveyed by the Bureau anticipate a negative IOD is likely to persist through November. By December, all models indicate a rapid decline of IOD index values, with three of five close to or outside of the threshold value.

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 during the first half of August 2022, with only a few periods of close to average anomalies during late May to mid-July 2022.

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 14 August 2022, sub-surface temperatures along the equator were mostly close to average. Between a depth of 750 m and 125 m in a region between 145°W and 120°W, temperatures were more than 3 degrees cooler than average. Compared to two weeks ago, this region of cool anomalies has increased in strength and moved eastwards.

The Bureau's ENSO Outlook has been raised to La Niña ALERT. This is due to both renewed cooling in the tropical Pacific Ocean as well as climate models indicating La Niña is likely during the austral spring and early summer. Historically, when La Niña ALERT criteria have been met, La Niña has subsequently developed around 70% of the time; this is approximately triple the normal likelihood. La Niña events increase the chances of above-average rainfall for northern and eastern Australia during spring and summer.

El Niño–Southern Oscillation (ENSO) ocean indicators are currently at neutral levels but show a renewed push towards La Niña. Central tropical Pacific sea surface temperatures (SSTs) have cooled over the past six weeks, while the sub-surface has also seen recent cooling. Some atmospheric indicators, such as the Southern Oscillation Index and cloudiness near the Date Line continue to show a La Niña-like signal.

Four of seven climate models surveyed by the Bureau suggest La Niña could return by early-to-mid spring. The remaining three models maintain a neutral, though cooler than average, outlook for central Pacific SSTs for the remainder of 2022.

The negative Indian Ocean Dipole (IOD) event continues. The IOD index has been very close to or within negative IOD thresholds (i.e. at or below −0.4 °C) since early June, with the latest weekly value one of the strongest observed so far during this event. All surveyed climate models indicate that negative IOD conditions are likely to continue into late spring. A negative IOD event is typically associated with above average winter–spring rainfall for much of Australia.

The Southern Annular Mode (SAM) index is currently neutral and is likely to be mostly positive for the coming three months. During the spring months, positive SAM has a drying influence for western Tasmania, with a wetter influence for NSW and far eastern Victoria.

The Madden–Julian Oscillation (MJO) is currently weak. Several models suggest the MJO is likely to strengthen in the coming days over Africa or the eastern Indian Ocean and progress eastwards, with the remaining models generally remaining weak or indiscernible. While over the African and eastern Indian Ocean regions, the MJO typically increases cloudiness in the eastern Indian Ocean, and decreases cloudiness for northern parts of the Maritime Continent.

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.

The Southern Annular Mode (SAM) index is currently neutral. Values are expected to be positive for the remainder of August, and generally positive throughout spring.

A positive SAM has a drying influence for parts of south-west and south-east Australia at this time of year, but increases the likelihood of rainfall in eastern New South Wales, far eastern Victoria, and parts of southern Queensland.

The El Niño–Southern Oscillation is currently neutral. However, recent climate model outlooks and current conditions have led to the Bureau's ENSO Outlook moving to La Niña ALERT, meaning there is around a 70% chance (three times the normal likelihood) of La Niña forming later in 2022.

Four of the seven surveyed international climate models predict neutral, but cooler than average, temperatures in the central tropical Pacific to persist through September, with three showing stronger cooling, reaching or exceeding the La Niña threshold value (−0.8 °C). By October, four of the seven models indicate SSTs in the central equatorial Pacific Ocean will exceed the La Niña threshold value.

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.