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

The SST map for April shows cooler than average SSTs extended along most of the eastern half of the equator in the Pacific Ocean, extending into the tropics along the coastline of South America. These cool anomalies were generally stronger in April than during March in the east of the basin, while in the central and western equatorial Pacific SSTs have returned to near average temperatures.

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

April values of the three key NINO indices were: NINO3 −0.4 °C, NINO3.4 −0.3 °C, and NINO4 −0.1 °C.

Sea surface temperatures (SST) for the tropical Pacific Ocean for the week ending 9 May were close to average across the equatorial Pacific Ocean.

Warm anomalies persist around the west and parts of the south coast of Australia, while around the Maritime Continent SSTs remain slightly warmer than average despite weakening of warm anomalies over the past two weeks.

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 9 May were: NINO3 −0. 1 °C, NINO3.4  −0.1 °C, and NINO4 +0.1 °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 9 May was +2.9. The 90-day SOI value was +3.5. 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 9 May were close to average across the most of tropical Pacific, but stronger than average west of the Date Line.

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 over the Indian Ocean and at moderate intensity. It is expected to weaken at it moves eastwards towards the Maritime Continent. When over the eastern Indian Ocean and Maritime Continent the MJO may enhance chances of above average rainfall over the Maritime Continent region. Additionally, it also typically acts to strengthen easterly winds in Queensland’s tropical east coast and increase temperatures across tropical Australia.

The Indian Ocean Dipole (IOD) is neutral. The latest weekly value of the IOD index to 9 May was +0.34 °C.

Weekly sea surface temperatures (SSTs) in the Indian Ocean were warmer than average across much of the southern half of the basin, and parts of the north close to the land masses.

Compared to two weeks ago, warm anomalies have strengthened in the north and weakened in the south of the basin. While generally remaining similar to two weeks ago close to Australia, warm anomalies around the north-west of Western Australia have strengthened. These warm anomalies near Australia may be influencing local weather patterns.

The strengthening of warm anomalies in the north-west of the basin has resulted in an increase in IOD index values over recent weeks, which may persist through May although models do not anticipate this lasting long enough to be considered an event. On the whole, most climate models expect neutral IOD for the first half of winter.

Three of the five surveyed climate models indicate a negative IOD may develop during winter or spring, although each model differs in the timing of a potential event.

It should be noted that individual models show a broad spread of likely scenarios, and that the accuracy of IOD forecasts made during autumn are lower than at other times of the year. Model accuracy improves for forecasts made during winter. The Bureau will continue to monitor model outlooks as the season proceeds and model skill improves.

Cloudiness near the Date Line was generally close to average during April, fluctuating around the mean, and has continued to fluctuate, being above average for the first part of May.

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 April) shows weak cool anomalies remain across the top 50 m of the central and eastern equatorial Pacific. The strength of these cool anomalies has decreased significantly compared to March, in line with the return to a neutral ENSO state.

Warm anomalies persist across parts of the column depth west of the Date Line. These warm anomalies have also decreased in strength and spatial extent compared to March.

For the five days ending 9 May, sub-surface temperatures were close to average across most of the equatorial Pacific, consistent with an ENSO neutral state. 

The El Niño–Southern Oscillation (ENSO) continues at neutral levels. Climate model outlooks currently indicate this neutral phase will last at least until October.

Oceanic indicators of ENSO persist at neutral levels, with Pacific sea surface temperatures close to the long-term average across most of the equatorial region. Beneath the surface, temperatures are near-average, with slightly warmer than average waters across much of the sub-surface. Atmospheric indicators such as the Southern Oscillation Index (SOI) and cloud patterns are also close to average. Trade winds have been stronger than average in the far west, but near average elsewhere.

The Madden–Julian Oscillation (MJO) is over the Indian Ocean region. It is forecast to move eastwards across Australian longitudes over the coming fortnight. When the MJO is active over the eastern Indian Ocean and Australian longitudes at this time of year, above average rainfall is more likely over the Maritime Continent to Australia's north. Additionally, it typically acts to strengthen easterly winds on Queensland’s tropical east coast and increase temperatures across tropical Australia.

The Southern Annular Mode (SAM) has been positive for the past week. It is expected to remain positive for the coming fortnight. SAM typically has little influence on Australian rainfall during autumn, but may have a drying influence for parts of south-west and south-east Australia over the coming fortnight.

The Indian Ocean Dipole (IOD) is currently neutral. Climate model outlooks suggest the IOD is most likely to remain neutral during the first half of winter. Three of the five models indicate negative IOD thresholds may be reached during winter or spring. The accuracy of IOD forecasts made during autumn is generally lower than at other times of the year, but improves in winter. A negative IOD increases the chances of above average winter-spring rainfall for much of southern 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.

The Southern Annular Mode (SAM) is currently positive and expected to remain positive for the next week then decline towards neutral over the following week. At this time of year positive SAM can reduce rainfall over south-west Western Australia and south-eastern Australia, but enhance rainfall for western parts of the coastline of the Great Australian Bight, New South Wales, and southern Queensland.

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.