Climate Driver Update
Climate drivers in the Pacific, Indian and Southern oceans and the Tropics
Sea surface temperature maps
Sea surface temperature maps are not available for forecasts before Spring 2018
SST outlooks for the next 3 months
ENSO is the oscillation between El Niño and La Niña states in the Pacific region. El Niño typically produces drier seasons, and La Niña drives wetter years, but the influence of each event varies, particularly in conjunction with other climate influences.
International climate model forecasts
The graphs are based on the ensemble mean for the most recent model run.
These graphs show the average forecast value of NINO3.4 for each international model surveyed for the selected calendar month. If the bars on the graph are approaching or exceeding the blue dashed line, there is an increased risk of La Niña. Similarly, if the bars on the graph are approaching or exceeding the red dashed line, there is an increased chance of El Niño.
Weekly sea surface temperatures
Graphs of the table values
Monthly sea surface temperatures
Graphs of the table values
5-day sub-surface temperatures
- See also: Links open in new window
- Animation of recent sub-surface temperature changes
- Archive of sub-surface temperature charts
Southern Oscillation Index
- Data Source: Links open in new window
- TAO/TRITON data
Cloudiness near the Date Line
About El Niño and La Niña (ENSO)
ENSO is the oscillation between El Niño and La Niña conditions.
The term El Niño refers to the extensive warming of the central and eastern tropical Pacific Ocean which leads to a major shift in weather patterns across the Pacific. This occurs every three to eight years and is associated with a weaker Walker Circulation (see diagram below) and drier conditions in eastern Australia. El Niño Southern Oscillation(ENSO) is the term used to describe the oscillation between the El Niño phase and the La Niña, or opposite, phase.
In the eastern Pacific, the northward flowing Humbolt current brings cooler water from the Southern Ocean to the tropics. Furthermore, along the equator, strong east to southeasterly Trade winds cause the ocean currents in the eastern Pacific to draw water from the deeper ocean towards the surface, helping to keep the surface cool. However in the far western Pacific there is no cool current, and weaker Trades mean that this "upwelling" effect is reduced. Hence waters in the western equatorial Pacific are able to warm more effectively under the influence of the tropical sun. This means that under "normal" conditions the western tropical Pacific is 8 to 10°C warmer than the eastern tropical Pacific. While the ocean surface north and northeast of Australia is typically 28 to 30°C or warmer, near South America the Pacific Ocean is close to 20°C. This warmer area of ocean is a source for convection and is associated with cloudiness and rainfall.
However, during El Niño years, the trade winds weaken and the central and eastern tropical Pacific warms up. This change in ocean temperature sees a shift in cloudiness and rainfall from the western to the central tropical Pacific Ocean.
The Southern Oscillation Index, or SOI, gives an indication of the development and intensity of El Niño or La Niña events in the Pacific Ocean. The SOI is calculated using the pressure differences between Tahiti and Darwin. The following figure demonstrates the typical fluctuations in SOI over a period of 11 years. Positive SOI values are shown in blue, with negative in orange. Sustained positive values are indicative of La Niña conditions, and sustained negative values indicative of El Niño conditions.
This graph shows the values of the SOI between 1991 and mid-2015. Monthly SOI data.
Each phase of the ENSO has a very different effect on the Australian climate. Events generally have an autumn to autumn pattern of evolution and decay. That is, they typically begin to develop during autumn, strengthen in winter/spring, then decay during summer and autumn of the following year. These effects are described in further detail on the following pages: El Niño and La Niña.
Further information about the El Niño Southern Oscillation and its impact on the Australian Climate.
The Climate Driver Update provides the latest information on the state of ENSO and the likely effect this will have on Australia.
Timeline of monthly Southern Oscillation Index (SOI) values since 1876
The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperatures between the eastern and western tropical Indian Ocean. A negative phase typically sees above average winter-spring rainfall in Australia, while a positive phase brings drier than average seasons.
International climate model forecasts
The graphs are based on the ensemble mean for the most recent model run.
Thse graphs show the average forecast value of the IOD index for each international model surveyed for the selected calendar month. If the majority of models are approaching or exceeding the blue dashed line, then there is an increased risk of a negative IOD event. If the majority of models are approaching or exceeding the red dashed line, then there is an increased risk of a positive IOD event.
About the Indian Ocean Dipole (IOD)
Indian Ocean sea surface temperatures impact rainfall and temperature patterns over Australia. Warmer than average sea surface temperatures can provide more moisture for frontal systems and lows crossing Australia.
Indian Ocean Dipole
Sustained changes in the difference between sea surface temperatures of the tropical western and eastern Indian Ocean are known as the Indian Ocean Dipole or IOD. The IOD is one of the key drivers of Australia's climate and can have a significant impact on agriculture. This is because events generally coincide with the winter crop growing season. The IOD has three phases: neutral, positive and negative. Events usually start around May or June, peak between August and October and then rapidly decay when the monsoon arrives in the southern hemisphere around the end of spring.
Indian Ocean Dipole years
The Southern Annular Mode, or SAM, refers to the north-south shift of rain-bearing westerly winds and weather systems in the Southern Ocean compared to the usual position.
Southern Annular Mode (SAM) history
About the Southern Annular Mode (SAM) forecast
The Southern Annular Mode can result in enhanced rainfall in regions of southern Australia.
The Southern Annular Mode, or SAM, also known as the Antarctic Oscillation (AAO), is a mode of variability which can affect rainfall in southern Australia. The SAM refers to the north/south movement of the strong westerly winds that dominate the middle to higher latitudes of the Southern Hemisphere. The belt of strong westerly winds in the Southern Hemisphere is also associated with the storm systems and cold fronts that move from west to east.
During the summer and autumn months (December through to May) the SAM is showing an increasing tendency to remain in a positive phase, with westerly winds contracted towards the south pole.
The contribution that the SAM makes to the climate variability in Australia and the apparent positive trend in the SAM are relatively recent discoveries and as such are still active areas of research.
The diagram above shows the area affected by the Southern Annular Mode, when it occurs and how long it may last.
In terms of mean sea level pressure, the SAM affects the coastal regions of southern Australia throughout the year. Extreme negative phases of the SAM can cause increased rainfall and cold air outbreaks in southern Australia.
Each SAM event, both positive and negative, tends to last for around ten days to two weeks. The time frame between positive and negative events however is quite random, but is typically in the range of a week to a few months.
The impact that the SAM has on rainfall varies greatly depending on season and region. If Australia were a few degrees further south, then the impact of changes in SAM would be much more pronounced. The diagram below describes the average impact on rainfall during a "positive" (westerly winds further south) SAM event.
The SAM also has an impact on temperatures. In general, in areas where rainfall is increased, temperature is decreased whilst where rainfall is decreased, temperature is increased.
The diagram above shows the impact that a "positive" SAM event (decreased westerly winds) has on Australian rainfall. Shading indicates daily rainfall anomaly in mm/day for each of the seasons. (Source: Hendon et al. 2007)
During July 2007, the SAM was in a strong negative phase. This was reflected in rainfall patterns across southern Australia.
- Find the latest SAM information in the Climate Driver Update Southern Ocean section
- Have a look at the latest atmospheric circulation patterns.
The Madden–Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. It can be characterised as an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days.
Tropical Climate Update
MJO phase diagram
*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.
The MJO phase diagram illustrates the progression of the MJO through different phases, which generally coincide with locations along the equator around the globe. RMM1 and RMM2 are mathematical methods that combine cloud amount and winds at upper and lower levels of the atmosphere to provide a measure of the strength and location of the MJO. When the index is within the centre circle the MJO is considered weak, meaning it is difficult to discern using the RMM methods. Outside of this circle the index is stronger and will usually move in an anti-clockwise direction as the MJO moves from west to east. For convenience, we define 8 different MJO phases in this diagram.
Daily averaged OLR anomalies
Westerly wind anomalies
Time-longitude plots of daily averaged OLR anomalies (left) and 850 hPa (approximately 1.5 km above sea level) westerly wind anomalies (right) are useful for indicating the movement of the MJO.
How to read the Time-Longitude plots
The vertical axis represents time with the most distant past on the top and becoming more recent as you move down the chart. The Horizontal axis represents longitude.
Eastward movement of a strong MJO event would be seen as a diagonal line of violet (downward from left to right) in the OLR diagram, and a corresponding diagonal line of purple in the wind diagram. These diagonal lines would most likely fall between 60°E and 150°E and they would be repeated nearly every 1 to 2 months.
About the Madden–Julian Oscillation (MJO) forecast
The Madden-Julian Oscillation is associated with weekly to monthly periods of enhanced and suppressed rainfall over parts of Australia.
The Madden-Julian Oscillation (MJO) is a global-scale feature of the tropical atmosphere.
The MJO is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterized as an eastward moving "pulse" of cloud and rainfall near the equator that typically recurs every 30 to 60 days. However, the signal of the MJO in the tropical atmosphere is not always present.
MJO effects are most evident over the Indian Ocean and western equatorial Pacific. It influences the timing, development and strength of the major global monsoon patterns, including the Indian and Australian monsoons.
Tropical cyclones are also more likely to develop in association with certain phases of a strong MJO event.
The MJO is associated with variations in wind, cloudiness, and rainfall. Most tropical rainfall comes from tall thunderstorms which have very cold tops. Thunderstorms that have cold tops emit only low levels of longwave radiation. Therefore, the MJO can be monitored by using satellite measurements of outgoing longwave radiation (OLR) to identify areas of cloudiness (low OLR) within the tropics.
The diagram above shows the area most affected by the Madden-Julian Oscillation (MJO), the seasons during which the MJO's influence on Australia is greatest, and for how long each active phase of the MJO typically lasts.
The MJO has its greatest effect on the tropical areas of Australia during summer. It may have some effect on parts of southern Australia, however this impact appears small when compared to the effect on northern regions, and remains the subject of research.
The MJO can have an effect on the timing and intensity of "active" monsoon periods in northern Australia. This can lead to enhanced rainfall - in both the intensity of the rainfall and the duration of the rainfall.
During late January 2006, an active phase of the MJO coincided with an active monsoon period, resulting in enhanced rainfall over northern Australia.
The following links provide further information on the MJO.
- The Tropical Climate Update provides information on the current phase of the MJO.
- Technical information and maps relating to the Real-time Multivariate MJO Index, which is a way of monitoring the climate and weather variations caused by the MJO. Please note that this product is a research product, and as such is not always updated and may be under-going continual changes as it is developed.
SSTs for December 2022 were cooler than average across the central and eastern tropical Pacific Ocean, extending from around 170°E to the South American coastline and across an area south of the equator to 20°S in the east of the basin.
Warm anomalies, up to 2 °C above the 1961–1990 average, were observed across waters to the north-east of Australia, particularly in the Coral Sea.
Weak warm anomalies have appeared to the west of Australia while cool anomalies have formed off the eastern coast of Australia, southwards of the Gold Coast.
Warm anomalies extend into the mid-latitudes in the southern Pacific and across the mid- to high latitudes in the north—a pattern characteristic of well-developed La Niña.
Cool anomalies for December were reduced in strength compared to those in November, especially just south of the equator. Warm anomalies to the north-east and south-east of Australia have also reduced in strength.
For the week ending 29 January 2023, sea surface temperatures (SST) were cooler than average across the central and parts of the eastern tropical Pacific Ocean (from the coast of South America to 170°E), although anomalies were generally less than 1 degree cooler than average.
Warm SST anomalies continue in the far west of the Pacific, especially to the north-west of Papua New Guinea, and in a band across the South Pacific from around New Caledonia and Fiji to the South American coast around 40°S.
Compared to two weeks ago, cool SST anomalies in the central equatorial Pacific have continued to weaken, especially between 170°W and 140°W. This is consistent with a weakening La Niña.
SSTs over the Coral Sea (to the north-east of Australia) are slightly warmer than average, while stronger warm anomalies continue to the south of Australia, especially around Tasmania and in waters close to New Zealand. Cool anomalies off the Kimberley and Pilbara coasts of Western Australia have largely dissipated.
The latest values of the three NINO indices for the week ending 29 January 2023 were: NINO3 −0.4 °C, NINO3.4 −0.6 °C, and NINO4 −0.5 °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 29 January 2023 was +12.9 while the 90-day SOI value was also +12.9. The 30-day SOI has decreased over the last fortnight while the 90-day SOI has remained relatively similar.
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 29 January 2023 were stronger than average in the western tropical Pacific Ocean. Elsewhere, trade wind strength was close to average.
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 MJO is in the eastern Indian Ocean and is moderate to strong in strength. Most models expect it to move into the Maritime Continent and towards the western Pacific in the coming week, with a possible decline in strength. While active over the Maritime Continent, the MJO may increase rainfall over northern Australia and may also lead to an increased chance of a monsoon burst returning to the northern Australia.
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 (typically December to April). The IOD index value for the week ending 29 January 2023 was −0.06 °C; within neutral bounds (between −0.4 °C and +0.4 °C).
Sea surface temperatures (SSTs) are generally close to average across most of the tropical Indian Ocean.
All five international climate models surveyed by the Bureau anticipate neutral values of the IOD index will continue through summer and into the southern hemisphere autumn.
Cloudiness near the Date Line has been mostly below average (i.e. positive outgoing longwave radiation (OLR) anomalies) since June 2021 with values over the last fortnight well below average.
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 26 January 2023) shows cool anomalies in the eastern half of the equatorial Pacific, from the surface to around 150 m depth. Anomalies reached more than 2 °C cooler than average across much of the region east of 115°W to around 100 m depth.
Warm anomalies are in place between around 50 and 250 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, warm anomalies have increased in strength during January and have expanded towards the central equatorial Pacific, while cool anomalies have decreased in strength.
For the five days ending 29 January 2023, sub-surface temperatures were warmer than average across the western and central equatorial Pacific at moderate depths, reaching more than 4 °C warmer than average around 150 to 200 m depth, from 165°W to the west of the basin. A small area of cooler than average temperatures persists in the eastern equatorial Pacific around 75 to 150 m depth east of 130°W. These are weaker than those in the western equatorial Pacific, reaching around 2 °C cooler than average.
Compared to two weeks ago, warm anomalies in the western Pacific sub-surface have increased in extent, reaching further into the central equatorial Pacific.
La Niña continues in the tropical Pacific, but oceanic indicators (sea surface temperatures, SSTs) have weakened since their peak during spring 2022. While ocean temperatures have eased from La Niña thresholds, the atmosphere has yet to respond, and remains La Niña-like. La Niña typically increases the chance of above-average rainfall for northern and eastern Australia during summer.
All models anticipate SSTs in the central Pacific will return to neutral ENSO levels during February, with neutral conditions (neither La Niña nor El Niño) anticipated until at least mid-autumn. As accuracy is generally lower for long-range ENSO forecasts made during summer, ENSO outlooks that extend past autumn should be viewed with caution.
The Southern Annular Mode (SAM) is currently strongly positive, but is anticipated to ease over the coming fortnight and then remain neutral over the remainder of February. During summer, positive SAM is typically associated with an increased chance of above average rainfall for eastern New South Wales, eastern Victoria, and north-east Tasmania, and below average rainfall for western Tasmania.
The Madden–Julian Oscillation (MJO) is currently moderate to strong and over the eastern Indian Ocean. Most models expect it to move across the Maritime Continent and towards the western Pacific in the coming week, with a possible decline in strength. While in the Maritime Continent, the MJO may increase the chance of an active monsoon period in northern Australia.
Sea surface temperatures are warmer than average to the south and south-east of Australia from the Eyre Peninsula to east of New Zealand, while generally weak warm anomalies persist across the west and north of the Maritime Continent. Warmer waters around Australia, especially in the tropics, can result in greater evaporation, humidity, cloudiness, and rainfall.
The Indian Ocean Dipole (IOD) is neutral and has little influence on Australian climate while the monsoon trough is in the southern hemisphere (typically December to 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.
The Southern Annular Mode (SAM) index has been strongly positive during the past week, and for much of summer despite a brief period of neutral values around 21 January 2023. .
The persistence of a positive phase of the SAM is in part associated with the current La Niña.
In summer months, a positive SAM increases the chance of above average rainfall for parts of north-east Tasmania, eastern Victoria, eastern New South Wales, and south-eastern Queensland, but increases the chance of below average rainfall for western Tasmania.
La Niña continues in the tropical Pacific. While Pacific Ocean temperatures have warmed in recent weeks, atmospheric indicators have yet to respond. The Bureau's ENSO Outlook continues at LA NIÑA.
All of the seven international climate models surveyed by the Bureau anticipate central Pacific sea-surface temperatures will be ENSO-neutral during February.
ENSO events typically peak in late (southern hemisphere) summer and decay during the autumn; current outlooks indicate this La Niña may decay slightly earlier than usual.
La Niña events typically increase the chance of above-average rainfall for northern and eastern Australia during summer. Even as La Niña weakens, it can continue to influence global weather and climate.
ENSO is not the only driver influencing Australia's climate. Other factors such as warmer than average SSTs close to Australia are also likely contributing to current outlooks. The Bureau's long-range forecast indicates a moderate chance of above average rainfall for some parts of eastern Australia over the next three months.
Product code: IDCKGEWW00