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


Average of international model outlooks for NINO3.4

Average of international model outlooks for IOD


Sea surface temperature maps

Sea surface temperature maps are not available for forecasts before Spring 2018

Global sea surface temperature outlooks for the months and season ahead. Anomalies indicate the difference from normal.

Sea surface temperature maps (select map for larger view)

SST outlooks for the next 3 months

Pacific Ocean

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.

NINO3.4 SST plumes from Bureau model forecasts, updated daily
Select to see full-size map of NINIO3.4 SST plumes from Bureau model forecasts, updated daily.

International climate model outlooks

Nino 3.4 2 month outlook
Graph details

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

Monthly temperatures

Southern Oscillation Index

30-day SOI values for the past two years
Select to see full-size map of 30-day Southern Oscillation Index values for the past two years, updated daily.

Trade winds

5-day SST and wind anomaly from TAO/TRITON
Select to see full-size map of 5-day SST and wind anomaly from TAO/TRITON.

Cloudiness near the Date Line

About El Niño and La Niña (ENSO)

El Niño Southern Oscillation

At a glance

ENSO is the oscillation between El Niño and La Niña conditions.

This climate influence is related to:   El Niño   La Niña   The Australian Monsoon

What is it?

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.

Neutral ENSO phase

Trade winds push warm surface water to the west and help draw up deeper, cooler water in the east. The warmest waters in the equatorial Pacific build up to the north of Australia and that area become the focus for cloudiness and rainfall.

Map diagram of Neutral ENSO

La Niña

Trade winds strengthen, increasing the temperature of the warm water north of Australia. Cloudiness and rainfall north of Australia are enhanced, typically leading to above average winter–spring rainfall for eastern and central parts of the country, and a wetter start to the northern wet season.

Map diagram of Negative ENSO

El Niño

Trade winds weaken (or reverse) and warmer surface water builds up in the central Pacific. Cloudiness and rainfall north of Australia are supressed, typically leading to below average winter–spring rainfall for eastern parts of the country, and a drier start to the northern wet season.

Map diagram of Positive ENSO

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.

 

graph of SOI

This graph shows the values of the SOI between 1991 and mid-2015. Monthly SOI data.

 

How does it affect Australia?

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 and latest updates

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

Timeline graph of ENSO and SOI index

Sustained negative values (bottom/yellow) of the SOI below −7 may indicate El Niño, while sustained positive values above +7 may indicate La Niña. La Niña and El Niño events since 1900 are indicated on the graph.
Drag graph slider to see full history and y-axis scale.


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.

IOD SST plumes from Bureau model forecasts, updated daily
Select to see full-size map of IOD SST plumes from Bureau model forecasts, updated daily.

International climate model outlooks

Latest IOD outlook
Graph details

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.

  1. 1960
  2. 1961
  3. 1963
  4. 1964
  5. 1972
  6. 1974
  7. 1981
  8. 1982
  9. 1983
  10. 1989
  11. 1992
  12. 1994
  13. 1996
  14. 1997
  15. 1998
  16. 2006
  17. 2010
  18. 2012
  19. 2014
  20. 2015
  21. 2016
Since 1960, when reliable records of the IOD began, to 2016 there have been 11 negative IOD and 10 positive IOD events.

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.


Neutral IOD phase

Water from the Pacific flows between the islands of Indonesia, keeping seas to Australia's northwest warm. Air rises above this area and falls over the western half of the Indian Ocean basin, blowing westerly winds along the equator.

Temperatures are close to normal across the tropical Indian Ocean, and hence the neutral IOD results in little change to Australia's climate.

Map diagram of Neutral IOD

Positive IOD phase

Westerly winds weaken along the equator allowing warm water to shift towards Africa. Changes in the winds also allow cool water to rise up from the deep ocean in the east. This sets up a temperature difference across the tropical Indian Ocean with cooler than normal water in the east and warmer than normal water in the west.

Generally this means there is less moisture than normal in the atmosphere to the northwest of Australia. This changes the path of weather systems coming from Australia's west, often resulting in less rainfall and higher than normal temperatures over parts of Australia during winter and spring.

Map diagram of Positive IOD

Negative IOD phase

Westerly winds intensify along the equator, allowing warmer waters to concentrate near Australia. This sets up a temperature difference across the tropical Indian Ocean, with warmer than normal water in the east and cooler than normal water in the west.

A negative IOD typically results in above-average winter–spring rainfall over parts of southern Australia as the warmer waters off northwest Australia provide more available moisture to weather systems crossing the country.

Map diagram of Negative IOD


Indian Ocean Dipole years

  1. 1960
  2. 1961
  3. 1963
  4. 1964
  5. 1972
  6. 1974
  7. 1981
  8. 1982
  9. 1983
  10. 1989
  11. 1992
  12. 1994
  13. 1996
  14. 1997
  15. 1998
  16. 2006
  17. 2010
  18. 2012
  19. 2014
  20. 2015
  21. 2016
Since 1960, when reliable records of the IOD began, to 2016 there have been 11 negative IOD and 10 positive IOD events.

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) outlook

Southern Annular Mode

At a glance

The Southern Annular Mode can result in enhanced rainfall in regions of southern Australia.

This climate influence is related to:   ENSO   Frontal Systems

What is it?

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.

SAM summer negative phase

Map diagram of Neutral sam

SAM summer positive phase

Map diagram SAM summer positive phase

SAM winter negative phase

Map diagram of SAM winter negative phase

SAM winter positive phase

Map diagram of SAM winter positive phase

Where, when and for how long does it occur?

 

Where, when and for how long does the Southern Annular Mode occur?

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.

How does it affect Australia?

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.

 

diagram showing the impact of the SAM

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)

 

An example

rainfall deciles thumbnail image

During July 2007, the SAM was in a strong negative phase. This was reflected in rainfall patterns across southern Australia.

Read more.

Further information and latest updates

 

Page updated: 12 June 2019

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

Archive:     

*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

OLR Archive:   

Westerly wind anomalies

Winds Archive:

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) outlook

Madden-Julian Oscillation

At a glance

The Madden-Julian Oscillation is associated with weekly to monthly periods of enhanced and suppressed rainfall over parts of Australia.

This climate influence is related to:   The Australian Monsoon   Tropical Cyclones   Tropical Depressions

What is it?

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.

Where, when and for how long does it occur?

 

where, when and for how long does it occur?

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.

 

How does it affect Australia?

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.

An example

monthly rainfall deciles thumbnail image

During late January 2006, an active phase of the MJO coincided with an active monsoon period, resulting in enhanced rainfall over northern Australia.

Read more.

Further information and latest updates

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 August 2022 were cooler than average along the equator from around 160°E to around 110°W, and warmer than average around the Maritime Continent in the west and off the coast of South America in the east.

Compared to July, cool anomalies have strengthened in the eastern tropical Pacific, while warm anomalies persist in the west.

Values of the three key NINO indices for August 2022 were: NINO3 −0.2 °C, NINO3.4 −0.7 °C, and NINO4 −0.6 °C.

For the week ending 25 September 2022, sea surface temperatures (SST) in the tropical Pacific Ocean were cooler than average along much of the equator between 160°E and 90°W. Cool SST anomalies extend south of the equator in much of the central and eastern Pacific. A small area of warm anomalies remains in the eastern equatorial Pacific, between 90°W and the South American coastline. Warm SST anomalies continue over the Maritime Continent and around much of Australia.

Compared to two weeks ago, cool SST anomalies have strengthened in the eastern equatorial Pacific Ocean, while warm anomalies have increased around northern Australia and around the Maritime Continent.

The latest values of the three NINO indices for the week ending 25 September 2022 were: NINO3 −0.6 °C, NINO3.4 −0.7 °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 25 September 2022 was +19.2. The 90-day SOI value was +11.5.

Both the 30-day and 90-day SOI have 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 25 September 2022 were slightly stronger than average across the western .

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) signal has been weak for most of September. However, most models indicate a pulse of the MJO will develop over the Maritime Continent in the coming week and maintain moderate strength as it moves east towards the western Pacific in the following week.

While active in the Pacific at this time of the year, the MJO slightly increases the chance of above average rainfall over the eastern half of Australia.

A negative Indian Ocean Dipole is under way. The latest Indian Ocean Dipole (IOD) index value, for the week ending 25 September 2022, was −0.78 °C. The IOD index value has been at or below the negative IOD threshold (−0.4 °C) since June.

Small areas of cool anomalies are present in the north-west of the Indian Ocean basin close to the Horn of Africa, while warm SST anomalies continue across the east of the Indian Ocean, including in waters close to Indonesia and north-west Australia.

A negative IOD increases the chances of above average spring rainfall for most of the eastern two thirds of Australia. It also increases the chances of warmer nights for northern Australia, and cooler days for much of the eastern mainland.

All international climate models surveyed by the Bureau indicate a negative IOD event is likely to persist until at least the end of spring. By December, all models indicate a rapid decline of IOD index values. This is typical of the IOD cycle, as IOD events breakdown with the arrival of the Asian monsoon.

Cloudiness near the Date Line had been mostly below average (i.e. positive outgoing longwave radiation, or OLR, anomalies) since June 2021. There was a recent brief period of around average cloudiness during September 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 22 September 2022) shows cool anomalies from the surface to around 150 m depth in the central to eastern equatorial Pacific. Warm anomalies persist between around 100 m and 250 m depth west of the International Date Line.

Cool anomalies increased in the central to eastern equatorial Pacific sub-surface month-on-month until August with month-to-date September values being similar to those observed in August.

For the five days ending 26 September 2022, sub-surface temperatures along the equator were mostly within two degrees of average. Compared to two weeks ago, cool anomalies in the eastern sub-surface have decreased in extent and strength, moving towards the surface and to the east with temperatures more than two degrees cooler than average around 75 m depth at 125°W.

Warm anomalies in the west have expanded, with temperatures more than two degrees warmer than average from around 125 m and 175 m depth between 160°E and 175°W.

La Niña is underway in the tropical Pacific and the Bureau's ENSO Outlook remains at LA NIÑA.

La Niña increases the chance of above average rainfall for northern and eastern Australia during spring and summer.

Both atmospheric and oceanic indicators of the El Niño–Southern Oscillation (ENSO) are consistent with an established La Niña, including tropical Pacific sea surface temperatures, the Southern Oscillation Index (SOI), trade wind strength, and equatorial cloudiness.

Models indicate the La Niña may peak during spring and return to neutral conditions early in 2023. Sea surface temperatures in the tropical Pacific have weakened a little compared to two weeks ago while the SOI has continued to rise and is currently well above La Niña thresholds.

The negative Indian Ocean Dipole (IOD) event continues. The IOD index has satisfied negative IOD thresholds (i.e. at or below −0.4 °C) since June. Models indicate that the negative IOD is likely to persist at least until late spring. A negative IOD typically increases the chance of above average spring rainfall for most of the eastern two thirds of Australia.

When La Niña and negative IOD conditions combine, the likelihood of above average rainfall over Australia is further increased, particularly for the eastern half of the continent.

The Southern Annular Mode (SAM) is currently positive and is likely to remain generally positive throughout spring into early summer. During the spring months, positive SAM increases the chance of above average rainfall for parts of eastern New South Wales, eastern Victoria, and south-eastern Queensland, but has a drying influence for western Tasmania.

Most models indicate the Madden–Julian Oscillation (MJO) will strengthen over the Maritime Continent in the coming week and maintain moderate strength as it moves east towards the western Pacific. While active in the Pacific at this time of the year, the MJO increases the chance of above average rainfall over the eastern half of Australia.

Climate change continues to influence Australian and global climate. Australia's climate has warmed by around 1.47 °C for the 1910–2020 period. 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 positive, and it is likely to remain positive throughout much of spring.

A positive SAM during spring typically increases the chance of below-average rainfall in western Tasmania and above-average rainfall in eastern parts of New South Wales and Victoria and south-eastern Queensland.

A La Niña event is under way in the tropical Pacific and the Bureau's ENSO Outlook continues at LA NIÑA.

All seven surveyed international climate models show La Niña thresholds (−0.8 °C) will continue to be exceeded during October, with five exceeding the threshold until at least the end of 2022.

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

La Niña events increase the chance of above-average rainfall for northern and eastern Australia during spring and summer.

Product code: IDCKGEWW00

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