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


Average of international model forecasts for NINO3.4

Average of international model forecasts for IOD


Sea surface temperature maps

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

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

Sea surface temperature maps (select map for larger view)

SST forecasts 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 forecasts

Nino 3.4 2 month forecast
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

Map of Outgoing longwave radiation (OLR) anomalies from NOAA
Map of Outgoing longwave radiation anomalies

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 forecasts

Latest IOD forecast
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. 1967
  5. 1972
  6. 1975
  7. 1990
  8. 1992
  9. 1994
  10. 1996
  11. 1997
  12. 1998
  13. 2006
  14. 2010
  15. 2015
  16. 2016
  17. 2019
  18. 2022
Since 1960, when reliable records of the IOD began, to 2023,
there have been 9 moderate to strong negative IOD events and 9 moderate to strong 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. 1967
  5. 1972
  6. 1975
  7. 1990
  8. 1992
  9. 1994
  10. 1996
  11. 1997
  12. 1998
  13. 2006
  14. 2010
  15. 2015
  16. 2016
  17. 2019
  18. 2022
Since 1960, when reliable records of the IOD began, to 2023,
there have been 9 moderate to strong negative IOD events and 9 moderate to strong 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) forecast

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

 

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.

NOAA outgoing longwave radiation OLR source data changed on 18 September, requiring technical updates to our processes. Until we implement these changes, NOAA images will be displayed for the MJO (History to now) chart, the Latest OLR maps, and the Time longitude OLR chart. Regional cloudiness charts are temporarily unavailable.

These charts are updated more frequently than Climate Driver Update editions, so may be more current than the MJO issue text (above).

Forecast MJO location and strength

The chart shows the strength and progression of the MJO through 8 different areas along the equator around the globe.
Area 3 is north east of Australia, 4 and 5 are to the north (the Maritime Continent), and 6 is to the north east.

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 this index is within the centre circle the MJO is considered weak. 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.


Select to see full-size map of MJO phase, updated daily.

Madden–Julian Oscillation (MJO) phase chart

Tropical atmospheric waves

About tropical waves

MJO

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 or wave of cloud and rainfall near the equator that typically recurs every 30 to 60 days.

Other tropical waves in the atmosphere

In addition to the MJO, other large-scale atmospheric waves also occur in the tropics. The main ones are the convectively-coupled Kelvin wave (KW), equatorial Rossby wave (ER), and mixed Rossby-Gravity wave (MRG). They can provide further insight into the current tropical weather, such as the location and development of tropical cyclones, and what may occur over the coming days to weeks. These waves occur year-round, but typically have a greater influence on tropical weather in the Australian region during the wet-season months of October to April.

Kelvin wave (KW)

Equatorial Kelvin waves are alternating low and high pressure centres along the equator that move from west to east. For consistency with the theoretical structure of Kelvin waves, convection (leading to cloudiness and rainfall) near the equator should be on the western side of the low pressure regions. In contrast, clear conditions should be found on the eastern side of the low pressure. Like other atmospheric tropical waves, alternating zones of cloudiness and clear weather can be seen on satellite imagery in association with an active Kelvin wave. The waves move in the same direction as the Madden–Julian Oscillation, from west to east, but typically 2 to 3 times faster.

Per figure caption
Schematic depiction of the theoretical solution for an equatorial Kelvin wave in a dry, incompressible atmosphere

Equatorial Rossby (ER) wave

In theory there are several different equatorial Rossby waves. The most commonly seen atmospheric ER wave, and the one we discuss here, has high and low pressure regions centred at latitudes about 10 degrees north and south of the equator. To be consistent with theory, the lows and highs should form a symmetric pattern about the equator. Due to the wind flow around these high and low pressure regions, some regions along the equatorial zone favour cloud and rain formation, while other regions favour stable, clear conditions. On satellite imagery equatorial Rossby waves can often be identified due to the presence of cloud systems at similar longitudes on both sides of the equator. These cloud systems, in conjunction with the off-equatorial low pressure, can be the precursors to tropical cyclones on either side of the equator. While equatorial Rossby waves move at a speed close to that of a typical Madden–Julian Oscillation pulse, they move in the opposite direction—from east to west.

Per figure caption
Schematic depiction of the theoretical solution for an equatorial Rossby wave in a dry, incompressible atmosphere. Only one wavelength is drawn here.

Mixed Rossby-Gravity (MRG) wave

Like equatorial Rossby waves, mixed Rossby-Gravity waves also move towards the west, but MRG waves have their pressure centres arranged anti-symmetrically on either side of the equator. This means a low pressure centre on one side of the equator will be opposite a high pressure centre in the other hemisphere. Satellite analysis of mixed Rossby-Gravity waves shows favoured zones for deep convection, often with thunderstorm clusters, in an antisymmetric arrangement about the equator. Their speed of movement to the west is faster than that of an ER wave.

Per figure caption
Schematic depiction of the theoretical solution for a mixed Rossby-gravity wave in a dry, incompressible atmosphere (upper) and with moist convection (lower)

Images are from The COMET® Program, from Introduction to Tropical Meteorology.
The COMET® Website is at http://meted.ucar.edu/ of the University Corporation for Atmospheric Research (UCAR), sponsored in part through cooperative agreement(s) with the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce (DOC). © 1997–2021 University Corporation for Atmospheric Research. All Rights Reserved.

MJO waves
Tropical atmospheric wave maps

MJO location and strength

These graphs show the strength and progression of the MJO through 8 different areas along the equator around the globe.
Area 3 is north west of Australia, 4 and 5 are to the north (the Maritime Continent), and 6 is to the north east.

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 this index is within the centre circle the MJO is considered weak. 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.

Latest 40 day MJO phase chart from NOAA

MJO phase diagram

*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.

Average weekly rainfall probabilities

These maps show average weekly rainfall probabilities for each of the 8 MJO phases. Green shades indicate higher than normal expected rainfall, while brown shades indicates lower than normal expected rainfall.

Select the 'Wind' checkbox to also show the expected 850 hPa (approximately 1.5 km above sea level) wind anomalies. The direction and length of the arrows indicate the direction and strength of the wind anomaly. The darker the arrow, the more reliable the information is.

The relationship of the MJO with global weather patterns changes with the season.
Read more: The Combined Influence of the Madden–Julian Oscillation and El Niño–Southern Oscillation on Australian Rainfall.

Global maps of outgoing longwave radiation (OLR)

Global maps of outgoing longwave radiation (OLR) highlight regions experiencing more or less cloudiness. The top panel is the total OLR in Watts per square metre (W/m²) and the bottom panel is the anomaly (current minus the 1979-1998 climate average), in W/m². In the bottom panel, negative values (blue shading) represent above normal cloudiness while positive values (brown shading) represent below normal cloudiness.

Latest total and anomaly outgoing longwave radiation (OLR) from NOAA

Time longitude plots

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.

Daily averaged OLR anomalies from NOAA

Westerly wind anomalies


Sea surface temperatures (SSTs) for August 2023 were warmer than average over almost all of the equatorial Pacific Ocean. SST anomalies more than 0.8 °C warmer than the long term average (1961–1990) were present over much of the tropical Pacific, increasing to more than 3 °C warmer than average in the eastern tropical Pacific. Much of the southern Pacific was also warmer than average for August.

Compared to July, warm anomalies have strengthened across the central and western equatorial Pacific.

Warm SST anomalies also continued in the southern Tasman Sea, between south-east Australia and New Zealand, but have slightly decreased compared to last month. Warm anomalies have spread to surround most of eastern and south-eastern Australia. Compared to last month, SSTs have warmed, but remain close to average across much of the waters surrounding Western Australia.

Globally, April to August 2023 SSTs were warmest on record (since 1900) for their respective months. In the ERSSTv5 dataset, the global area-average SSTs for April, May, June, July and August were above their long term  (1961–1990) average by 0.69 °C, 0.70 °C, 0.71 °C, 0.80 °C and 0.75 °C, respectively. August 2023 SSTs were also the warmest globally for any month since observational records began in 1854.

For the week ending 24 September 2023, sea surface temperatures (SSTs) were warmer than average across almost all the equatorial region of the tropical Pacific Ocean. Anomalies were more than 2 °C warmer than average in the eastern tropical Pacific. Compared to last week, the strength and spread of warmth in the tropical Pacific remains similar. Atypical to a normal El Niño pattern, warm anomalies continue to persist in the south-west Pacific from the east of the Solomon Islands extending south-eastwards to Tahiti.

Closer to Australia, warmer than average waters persist along the east Australian coastline, with waters up to 2 °C above average along the north-and south-east coasts. There are also warm SST anomalies in patchy areas south-west of WA and in the southern Tasman Sea, from south-east Australia to the South Island of New Zealand. The past fortnight has seen warmer than average water appear off the northern WA coastline.

The latest values of the three NINO indices for the week ending 24 September 2023 were: NINO3, +1.82 °C; NINO3.4, +1.45 °C; and NINO4, +1.15 °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-, 60- and 90‐day Southern Oscillation Index (SOI) values for the period ending 24 September 2023 were −16.0, −13.1 and −10.2, respectively.

Sustained negative values of below −7 typically indicate El Niño, while sustained positive values above +7 typically indicate La Niña.

Trade winds for the 5 days ending 24 September 2023 were weaker than average in the far western equatorial Pacific, but generally close to average elsewhere.

Trade winds for August 2023 were slightly weaker than average across the equatorial Pacific for the first time since January 2020.

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

The Madden–Julian Oscillation (MJO) is currently weak or indiscernible. About half the models indicate it is likely to remain weak or indiscernible, while the other half suggest the MJO may strengthen and progress into the Maritime Continent and western Pacific over the coming fortnight.

A positive IOD event is underway. The Indian Ocean Dipole (IOD) index was +1.45 °C for week ending 24 September. This is its sixth week above the positive IOD threshold (+0.40 °C).

Weekly sea surface temperatures (SSTs) for the week ending 24 September show warmer than average waters close to the Horn of Africa. Conversely, the eastern pole of the IOD was cooler than average, with a notable area of cooler waters extending southwards from the coast of Java. This shows a clear gradient between the western and eastern tropical Indian Ocean that is typical of a positive IOD. Compared to last week, the cooling has expanded westwards from Java and the warm anomalies have slightly cooled over the western pole of the IOD.

All international climate models surveyed by the Bureau suggest the positive IOD event is likely to continue for the remainder of the southern hemisphere spring. A positive IOD typically leads to reduced spring rainfall for central and south-east Australia. When a positive IOD and El Niño occur together, their drying effect is typically stronger and more widespread across Australia.

Outgoing Longwave Radiation (OLR) near the Date Line has been below average for the past 30 days ending 24 September.

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

The 4-month sequence of equatorial Pacific sub-surface temperature anomalies (to 25 September 2023) shows warm anomalies across most of the top 150 m of the equatorial Pacific band, except in the far west. Anomalies increase in magnitude eastwards across the equatorial Pacific band, with the far west close to average and the eastern Pacific more than 2 °C warmer than average.

The past 3 months have seen sub-surface heat shift towards the eastern Pacific, between the surface and 150 m depth. During September, there has been a movement of warmth away from the South American coastline. However, warm anomalies in the eastern Pacific have decreased slightly. In the western Pacific, temperatures have decreased such that most of the water column is now close to average.

For the 5 days ending 24 September 2023, sub-surface temperatures were warmer than average across the upper levels of the equatorial Pacific between the surface to around 125 m depth. Much of this region was more than 2 °C warmer than average, with anomalies more than 5 °C warmer than average in a small area of the eastern Pacific.

Compared to last week, warm anomalies in the eastern and central Pacific have increased.

An El Niño and a positive IOD are underway.

Oceanic indicators firmly exhibit an El Niño state. Central and eastern Pacific sea surface temperatures (SSTs) continue to exceed El Niño thresholds. Models indicate further warming of the central to eastern Pacific is likely.

Broadscale pressure patterns over the tropical Pacific reflect El Niño, with the 90-day Southern Oscillation Index (SOI) at −10.2. Trade wind strength over the past week has weakened in the far western Pacific, but is close to normal elsewhere. Overall, there are signs that the atmosphere is responding to the warm SSTs over the Pacific and coupling of ocean and atmosphere is occurring. This coupling is a characteristic of an El Niño event and is what strengthens and sustains an event for an extended period. El Niño typically leads to reduced spring rainfall for eastern Australia.

Climate models indicate this El Niño is likely to persist until at least the end of February. El Niño typically leads to reduced spring and early summer rainfall for eastern Australia, and warmer days for the southern two-thirds of the country.

A positive Indian Ocean Dipole (IOD) is underway. The IOD index is +1.45 °C for week ending 24 September. This is its sixth week above the positive IOD threshold (+0.40 °C). All models predict this positive IOD will persist to at least the end of spring. A positive IOD typically leads to reduced spring rainfall for central and south-east Australia.

When a positive IOD and El Niño occur together, their drying effect is typically stronger and more widespread across Australia.

The Madden–Julian Oscillation (MJO) is currently weak or indiscernible. About half the models indicate it is likely to remain weak or indiscernible, while the other half suggest the MJO may strengthen and progress into the Maritime Continent and western Pacific over the coming fortnight.

The Southern Annular Mode (SAM) index is currently neutral with forecasts indicating it is likely to remain neutral over the coming fortnight.

The long-range forecast for Australia indicates warmer and drier than average conditions are likely across most of Australia from October to December. The Bureau's climate model takes into account all influences from the oceans and atmosphere when generating its long-range forecasts.

Global warming

Global warming continues to influence Australian and global climate. Global sea surface temperatures (SSTs) were warmest on record for their respective months during April to August 2023. August 2023 SSTs were also the warmest globally for any month since observational records began in 1850.

Australia's climate has warmed by an average of 1.48 ± 0.23 °C since national records began in 1910. There has also been a trend towards a greater proportion of rainfall from high intensity, short duration rainfall events, especially across northern Australia. Southern Australia has seen a reduction, by 10 to 20%, in cool season (April to October) rainfall in recent decades. This is due to a combination of natural variability on decadal timescales and changes in large-scale circulation caused by an increase in greenhouse gas emissions.

The Southern Annular Mode (SAM) index is currently neutral with forecasts indicating it is likely to remain neutral for the coming fortnight. During spring, a neutral SAM is associated with typical climate conditions for Australia.

Central and eastern Pacific sea surface temperatures (SSTs) currently exceed El Niño thresholds. International climate models suggest some further warming of the central and eastern tropical Pacific Ocean is likely. All surveyed models indicate SSTs will remain above El Niño thresholds until at least the end of the 2023–24 southern hemisphere summer.

Bureau long-range forecasts are for SSTs up to 2.5 °C warmer than average off eastern Tasmania and in the eastern Tasman Sea from October to the end of 2023.

El Niño typically increases the chance of below average winter–spring rainfall in eastern Australia and warmer than average days for the southern two-thirds of Australia.

Product code: IDCKGEWW00

Creative Commons By Attribution logo Unless otherwise noted, all maps, graphs and diagrams in this page are licensed under the Creative Commons Attribution 4.0 International Licence