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

The SST map for May shows SSTs were close to average across most of the equatorial Pacific Ocean, although cool anomalies remained in some small areas of the tropics in the east of the Basin, extending along the coastline of South America. These cool anomalies have weakened compared to April.

SSTs were warmer than average in waters around the west and much of the south of Australia.

May values of the three key NINO indices were: NINO3 −0.2 °C, NINO3.4 −0.1 °C, and NINO4 +0.1 °C.

Sea surface temperatures (SST) for the tropical Pacific Ocean for the week ending 6 June were close to average across the equatorial Pacific Ocean.

Warm anomalies persist around Western Australia and parts of the south and east coast of Australia, while around the Maritime Continent SSTs are generally close to average.

All three NINO indices are within the ENSO-neutral range. The latest values of the three NINO indices in the tropical Pacific for the week ending 6 June were: NINO3 +0. 1 °C, NINO3.4  0.0 °C, and NINO4 0.0 °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 30 days ending 6 June was −0.4. The 90-day SOI value was +1.9. Both are within ENSO-neutral thresholds.

Sustained negative values of the SOI below −7 typically indicate El Niño while sustained positive values above +7 typically indicate La Niña. Values between +7 and −7 generally indicate neutral conditions.

Trade winds for the 5 days ending 6 June were close to average across the tropical Pacific.

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

The Madden–Julian Oscillation (MJO) is currently weak and indiscernible. It is forecast to strengthen in the African sector by mid-June, but is unlikely to have significant influence on Australian rainfall at this time of year.

The Indian Ocean Dipole (IOD) is neutral. The latest weekly value of the IOD index to 6 June was −0.65 °C, the third consecutive week below the negative IOD threshold (−0.4 °C). While a negative IOD event is not declared until the index remains below the threshold for at least 8 weeks, this pattern can still influence Australian rainfall as the event develops, with wetter than average conditions in central and southern Australia more likely.

Weekly sea surface temperatures (SSTs) in the Indian Ocean were warmer than average across much of the southern and eastern halves of the basin, while small areas of cooler than average SSTs have emerged close to the Horn of Africa.

Some models suggest a negative IOD may develop in winter, with three of the five surveyed climate models indicating a negative IOD could develop during winter or early spring.

It should be noted that model accuracy during early June is still relatively low for IOD forecasts. Model accuracy will improve significantly by the end of the month. The Bureau will continue to monitor model outlooks as the season proceeds and model skill improves.

Cloudiness near the Date Line has fluctuated around the mean since the start of April, generally remaining close to average.

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

The four-month sequence of equatorial Pacific sub-surface temperature anomalies (to May) shows a pattern consistent with the return to a neutral ENSO state.

For May weak warm anomalies were present across much of the central and western equatorial Pacific, mostly between 75 m and 150 m depth.

For the five days ending 6 June, sub-surface temperatures were close to average across most of the equatorial Pacific, consistent with an ENSO neutral state. Warm anomalies in excess of 2 °C exist between the depths of 25 m and 100 m in the eastern Pacific.

The El Niño–Southern Oscillation (ENSO) remains neutral, with all oceanic and atmospheric indicators within the neutral range. Climate model outlooks show this neutral ENSO state is likely to continue until at least spring.

The Indian Ocean Dipole (IOD) is currently neutral, although the index has been below the negative IOD threshold for three consecutive weeks. Large parts of the eastern Indian Ocean are warmer than average, with some cooler than average water near the Horn of Africa. The consensus of international climate model outlooks suggest the IOD is most likely to remain neutral during the first part of winter, although three of the five models suggest negative IOD conditions could develop over winter or spring. The accuracy of IOD forecasts is still low in early June but will increase significantly by the end of the month. A negative IOD increases the chances of above average winter–spring rainfall for parts of southern Australia. While a negative IOD event is not declared until the index remains below the threshold for at least 8 weeks, the current pattern can still influence Australian rainfall as the event evolves.

The Madden–Julian Oscillation (MJO) is currently weak or indiscernible. It is forecast to re-appear over the African region during the next fortnight. Its effect on Australia for this period is expected to be weak. At this time of the year, the MJO influence is primarily in the northern hemisphere, and it therefore has less influence on northern Australia.

The Southern Annular Mode (SAM) has been neutral for the past week. It is expected to be positive for the coming fortnight. Positive SAM typically acts to decrease rainfall over south-west and south-east Australia and increase rainfall over parts of eastern Australia.

Climate change continues to influence Australian and global climate. Australia's climate has warmed by 1.44 ± 0.24 °C over 1910–2019, while southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.

Recent values of the Southern Annular Mode (SAM) index were close to neutral, however SAM is expected to be positive for the next two weeks. At this time of year positive SAM typically results in cold fronts and storm tracks shifting further south than their usual winter path. This can increase rainfall over parts of eastern Australia, but reduce rainfall for much of south-east South Australia, western and central Victoria, Tasmania, and the west coast of Western Australia.

The El Niño–Southern Oscillation (ENSO) is currently neutral. All of the international climate models surveyed by the Bureau anticipate NINO3.4 will remain neutral until at least October.