Climate Driver Update - Bureau of Meteorology
The El Niño–Southern Oscillation (ENSO) is currently neutral. Sea surface temperatures (SSTs) in the central equatorial Pacific Ocean are ENSO- ...
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- Climate Driver Update

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

[For long-range forecasts of rainfall and temperature for Australia, please see our long-range forecast page. It provides the best guidance on likely conditions in the coming months, using the Bureau's climate model to take into account all influences from the oceans and atmosphere when generating its long-range forecasts.\
\
![](/climate/promotion/images/arrow-circle.svg)\
\
![Rainfall long-range forecasts, includes text and audio](/clim_data/IDCK000078/latest/rain.forecast.median.national.season1.latest.hr.png?20240723)![Temperature long-range forecasts](/clim_data/IDCK000078/latest/tmax.forecast.median.national.season1.latest.hr.png?20240723)](/climate/outlooks/)

The Climate Driver Update provides information on the broader hemispheric climate state, such as the El Niño Southern Oscillation and Indian Ocean Dipole. This information provides additional context to the rainfall and temperature forecasts.


- [Overview](#overview-section)
- [Pacific Ocean](#pacific)
- [Indian Ocean](#indian)
- [Southern Ocean](#southern)
- [Tropics](#tropics)

- [Summary](#overview)
- [Sea surface](#overview-sst)

[ENSO Outlook status](/climate/enso/outlook/ "ENSO Outlook status")

### Average of international model forecasts for NINO3.4

This content is not available

### Average of international model forecasts for IOD

This content is not available

- **See also: Links open in new window**
- [About Australian climate influences](/climate/about/)
- [Climate model summary](/climate/model-summary/#region=NINO34&tabs=Pacific-Ocean)
- [Long-range forecast](/climate/ocean/outlooks/#region=NINO34 "Bureau model multi-month SST forecast")

## 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)

Month 1Month 2Month 3Season1

## SST forecasts for the next 3 months

## Pacific Ocean

- [Forecast](#enso-outlook)
- [Sea surface](#sst "Sea surface temperature")
- [Sea sub–surface](#subsurf)
- [SOI](#soi "South Oscillation Index")
- [Trade winds](#trades)
- [Cloudiness](#cloud)
- [History](#enso-history)
- [About](#enso-about)

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.](/climate/images/interface/unavailable.png)

### International climate model forecasts

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.

This content is not available

- **See also: Links open in new window**
- [ENSO Outlook status](/climate/enso/outlook/)
- [Climate model summary](/climate/model-summary/#region=NINO34&tabs=Pacific-Ocean)
- [Long-range forecast](/climate/ocean/outlooks/#region=NINO34 "Bureau model multi-month SST forecast")

## Weekly sea surface temperatures

Graphs of the table values

## Monthly sea surface temperatures

Graphs of the table values

[![Select to see full-size map showing temperature anomalies in the tropical Pacific](/climate/images/interface/unavailable.png)\
Weekly temperature anomalies in the tropical Pacific](/climate/enso/sst_weekly.gif?1726029721 "Weekly sea surface temperature anomalies in the tropical Pacific")

[![Map showing temperature anomalies in the tropical Pacific](/climate/images/interface/unavailable.png)\
Monthly temperature anomalies in the tropical Pacific](/climate/enso/sst_monthly.gif "Monthly sea surface temperature anomalies in the tropical Pacific")

- **See also: Links open in new window**
- Animation of recent SST changes
- [Weekly index graphs](/climate/enso/indices.shtml#bookmark=nino3.4 "Sea surface temperature index values")
- [Sea surface temperature maps](/climate/ocean/sst/ "Sea surface temperature maps")
- [Map of NINO and IOD regions](/climate/influences/images/map-indices.png "Map of NINO and IOD regions")

## 5-day sub-surface temperatures

## Monthly temperatures

[5-day sub-surface temperatures and anomalies\
![Select to see full-size plot of sub-surface temperatures and anomalies.](/climate/images/interface/unavailable.png)](/climate/enso/sub_surf_tao.gif?1726029721 "Plot of sub-surface temperatures and anomalies")

[Monthly sub-surface temperature anomalies\
![Select to see full-size plot of sub-surface temperature anomalies](/climate/images/interface/unavailable.png)](/climate/enso/sub_surf_mon.gif?1726029721 "Plot of sub-surface temperature anomalies")

- **See also: Links open in new window**
- Animation of recent sub-surface temperature changes
- [Sub-surface temperature charts, history](/oceanography/oceantemp/pastanal.shtml)

## 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.](/clim_data/IDCKGSM000/soi30.png?1726029721)

- **See also: Links open in new window**
- [Monthly SOI graph](/climate/enso/soi/)
- [30-day SOI values](/clim_data/IDCKGSM000/soi.txt?1726029721)

## 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.](/climate/images/interface/unavailable.png)

- **Data Source: Links open in new window**
- [TAO/TRITON data](http://www.pmel.noaa.gov/tao/jsdisplay/ "TAO/TRITON data")

## Cloudiness near the Date Line

[Graph of Outgoing longwave radiation (OLR) totals over the dateline\
![Select to see full-size graph of OLR totals over the dateline.](/climate/images/interface/unavailable.png)](/climate/mjo/graphics/region.ts.dateline.gif?1726029721 "Graph of OLR totals over the dateline")

## About El Niño and La Niña (ENSO)

El Niño Southern Oscillation

[![](https://img.youtube.com/vi/dzat16LMtQk/hqdefault.jpg)Video: Understanding ENSO. Described transcript available below](http://youtu.be/dzat16LMtQk "Video – Understanding ENSO")[ENSO video transcript](/climate/iod/images/understanding-iod.text)

[![Summary about El Niño in Australia](/climate/enso/images/nino-poster-tn.png)](/climate/enso/images/El-Nino-in-Australia.pdf "Summary about El Niño in Australia")[El Niño \
\
summary](/climate/enso/images/El-Nino-in-Australia.pdf "Summary about El Niño in Australia")[![Summary about La Niña in Australia](/climate/enso/images/nina-poster-tn.png)](/climate/enso/images/La-Nina-in-Australia.pdf "Summary about La Niña in Australia")[La Niña \
\
summary](/climate/enso/images/La-Nina-in-Australia.pdf "Summary about La Niña in Australia")

**Contents**

- [What is it?](#intro)
- [How does it affect Australia?](#how)
- [Further information and latest updates](#info)

## At a glance

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

_This climate influence is related to:   [El Niño](?bookmark=elnino) [La Niña](?bookmark=lanina) [The Australian Monsoon](?bookmark=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](?bookmark=walkercirculation) (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](#ensoNeutral)
- [La Niña](#ensoNegative)
- [El Niño](#ensoPositive)

### 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](/climate/about/australian-climate-influences/images/enso-neutral.png)](/climate/about/australian-climate-influences/images/enso-neutral.png "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](/climate/about/australian-climate-influences/images/enso-la-nina.png)](/climate/about/australian-climate-influences/images/enso-la-nina.png "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](/climate/about/australian-climate-influences/images/enso-el-nino.png)](/climate/about/australian-climate-influences/images/enso-el-nino.png "Positive ENSO")

The Southern Oscillation Index, or SOI, gives an indication of the development and intensity of El Niño or La Niña 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.

## How does it affect Australia?

Each phase of the ENSO has a very different effect on the Australian climate. El Niño and La Niña 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](?bookmark=elnino) and [La Niña](?bookmark=lanina).

## Further information and latest updates

Further information about the El Niño Southern Oscillation and its impact on the Australian Climate.

### Timeline of monthly Southern Oscillation Index (SOI) values since 1876

![Timeline graph of ENSO and SOI index](/climate/influences/timeline/enso/monthly-soi.png)

Sustained negative values (bottom/yellow) of the SOI below −7 may indicate El Niño, while sustained positive values (top/blue) 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_.

- **More history:**
- [Past El Niño and La Niña events](/climate/history/enso/)
- [2010–11 and 2011–12 La Niña events](/climate/enso/history/ln-2010-12/)

- [El Niño impacts](#elnino)
- [La Niña impacts](#lanina)

- [Rainfall and Temperature](/climate/enso/content/nino-rain-temp.shtml)
- [Event evolution](/climate/enso/content/nino-cycle.html)

- [Rainfall and Temperature](/climate/enso/content/nina-rain-temp.shtml)
- [Event evolution](/climate/enso/content/nina-cycle.html)

- [Forecast](#iod-outlook)
- [Sea surface](#iod-sst)
- [History](#iod-history)
- [About](#iod-about)

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.](/climate/images/interface/unavailable.png)

### International climate model forecasts

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.


This content is not available

- **See also: Links open in new window**
- [Climate model summary](/climate/model-summary/#tabs=Indian-Ocean)
- [Long-range forecast](/climate/ocean/outlooks/#region=IOD "Bureau model multi-month SST forecast")

## Weekly sea surface temperatures

![Weekly temperature anomalies in the tropical Indian Ocean](/climate/images/interface/unavailable.png)Weekly temperature anomalies in the tropical Indian Ocean

## Monthly sea surface temperatures

![Monthly temperature anomalies in the tropical Indian Ocean](/climate/images/interface/unavailable.png)Monthly temperature anomalies in the tropical Indian Ocean

- **See also: Links open in new window**
- [SST timeseries graphs](/climate/enso/indices.shtml?bookmark=iod "Sea surface temperature index values")
- [Sea surface temperature maps](/climate/ocean/sst/ "Sea surface temperature maps")
- [Map of NINO and IOD regions](/climate/influences/images/map-indices.png "Map of NINO and IOD regions")

01. 1960
02. 1961
03. 1963
04. 1967
05. 1972
06. 1975
07. 1990
08. 1992
09. 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.


- [Positive IOD impacts](#positive)
- [Negative IOD impacts](#negative)
- [Pacific Ocean interaction](#interaction)

- [Rainfall and Temperature](/climate/iod/content/iodpos-rain-temp.shtml)
- [Example positive IOD event](/climate/iod/content/example-positive-iod.html)
- [Event evolution](/climate/iod/content/iodpos-cycle.html)

- [Rainfall and Temperature](/climate/iod/content/iodneg-rain-temp.shtml)
- [Example negative IOD event](/climate/iod/content/example-negative-iod.html)
- [Event evolution](/climate/iod/content/iodneg-cycle.html)

- [IOD and ENSO interaction](/climate/iod/content/years-iod-enso.html)
- [Positive IOD and El Niño](/climate/iod/content/iodpos-nino.html)
- [Negative IOD and La Niña](/climate/iod/content/iodneg-nina.html)

## About the Indian Ocean Dipole (IOD)

[![](https://img.youtube.com/vi/J6hOVatamYs/hqdefault.jpg)Video: Understanding IOD. Described transcript available below](https://youtu.be/J6hOVatamYs "Video – Understanding the IOD")[IOD video transcript](/climate/iod/images/understanding-iod.text)

[![](/climate/iod/images/poster.png)](/climate/iod/images/IOD-in-Australia.pdf "IOD summary information as PDF, opens in new screen")
IOD summary (PDF 4MB) [Read poster as text](/climate/iod/images/iod-in-australia-long.txt)

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](#iodNeutral)
- [Positive IOD phase](#iodPositive)
- [Negative IOD phase](#iodNegative)

### 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](/climate/about/australian-climate-influences/images/iod-neutral.png)](/climate/about/australian-climate-influences/images/iod-neutral.png "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](/climate/about/australian-climate-influences/images/iod-positive.png)](/climate/about/australian-climate-influences/images/iod-positive.png "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](/climate/about/australian-climate-influences/images/iod-negative.png)](/climate/about/australian-climate-influences/images/iod-negative.png "Negative IOD")

## Indian Ocean Dipole years

01. 1960
02. 1961
03. 1963
04. 1967
05. 1972
06. 1975
07. 1990
08. 1992
09. 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.


- **See also:** Links open in new window
- [Indian Ocean Dipole outlook](/climate/enso/#tabs=Indian-Ocean "Indian Ocean Dipole outlooks")
- [Indian Ocean outlook model summary](/climate/model-summary/#tabs=Indian-Ocean "Indian Ocean climate model summary")
- [Graph of latest IOD Index](/climate/enso/indices.shtml?bookmark=iod "Indian Ocean graph")

- [Forecast](#sam-outlook)
- [History](#sam-history)
- [About](#sam-about)

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.

### This automated graph is updated more frequently than the fortnightly text. The SAM can change quickly. Graphs corresponding to the text issue date can be viewed in the [Climate Driver Update history](/climate/enso/wrap-up/archive.shtml)

Daily Southern Annular Mode (SAM) index values
![SAM index forecast chart with daily values](/climate/images/interface/unavailable.png)

## Southern Annular Mode (SAM) history

- [SAM in winter](#sam-winter)
- [SAM in summer](#sam-summer)

- [Climate effects](/climate/sam/content/samwinter-rain.html)
- [Example positive winter SAM event](/climate/sam/content/example-positive-winter-sam.html)
- [Example negative winter SAM event](/climate/sam/content/example-negative-winter-sam.html)

- [Climate impacts](/climate/sam/content/samsummer-rain.html)
- [Example positive summer SAM event](/climate/sam/content/example-positive-summer-sam.html)
- [Example negative summer SAM event](/climate/sam/content/example-negative-summer-sam.html)

## About the Southern Annular Mode (SAM) forecast

Southern Annular Mode

**Contents**

- [What is it?](#intro)
- [Where, when and for how long does it occur?](#where)
- [How does it affect Australia?](#how)
- [An example](#eg)

## At a glance

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

_This climate influence is related to:   [ENSO](?bookmark=enso) [Frontal Systems](?bookmark=fronts)_

[![](https://img.youtube.com/vi/KrhWsXCB3u8/hqdefault.jpg)](https://youtu.be/KrhWsXCB3u8 "Video – Understanding the SAM")[![](/climate/sam/images/SAM-in-Australia.png)](/climate/sam/images/SAM-in-Australia.pdf "SAM summary information as PDF, opens in new screen")

* * *

## 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.

- [Summer negative](#summerNeg)
- [Summer positive](#summerPos)
- [Winter negative](#winterNeg)
- [Winter positive](#winterPos)

### SAM summer negative phase

[![Map diagram of Neutral sam](/climate/about/australian-climate-influences/images/sam-summer-negative.png)](/climate/about/australian-climate-influences/images/sam-summer-negative.png "Neutral sam")

### SAM summer positive phase

[![Map diagram SAM summer positive phase](/climate/about/australian-climate-influences/images/sam-summer-positive.png)](/climate/about/australian-climate-influences/images/sam-summer-positive.png "SAM summer positive phase")

### SAM winter negative phase

[![Map diagram of SAM winter negative phase](/climate/about/australian-climate-influences/images/sam-winter-negative.png)](/climate/about/australian-climate-influences/images/sam-winter-negative.png "SAM winter negative phase")

### SAM winter positive phase

[![Map diagram of SAM winter positive phase](/climate/about/australian-climate-influences/images/sam-winter-positive.png)](/climate/about/australian-climate-influences/images/sam-winter-positive.png "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?](/climate/cdo/education/sam/sam_info.gif)

_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](/climate/cdo/education/sam/impact.gif)

_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](https://journals.ametsoc.org/view/journals/clim/20/11/jcli4134.1.xml))_

## An example

[![rainfall deciles thumbnail image](/climate/cdo/education/sam/decile_small.gif)](?bookmark=samexample)

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

[Read more.](?bookmark=samexample)

- [MJO forecast](#mjoOutlook)
- [History to now](#phaseSection)
- [Averages](#averagesSection)
- [Cloudiness](#cloudSection)
- [Time longitude](#timelongSection)
- [About](/climate/mjo/about-mjo.shtml)

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.

## This tropical information is moving

Tropical outlooks are now available in [Tropical monitoring](/climate/mjo/). The Tropics section of the Climate Driver Update will be removed by October.

**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 west of Australia, 4 and 5 are to the north (the [Maritime Continent](/climate/about/tropics/maritime-continent.html)), 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.


## 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](/climate/enso/wrap-up/images/eq_kelvin_wave.png)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](/climate/enso/wrap-up/images/eq_rossby_wave.png)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](/climate/enso/wrap-up/images/mixed_rossby_gravity.png)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.

MJOKelvin waveEquatorial Rossby waveMRG wavePeriodMJO 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](#tabs=About)), 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 days90 days Archive

Months
Jan–MarApr–JunJul–SepOct–DecYear


![MJO phase diagram](/clim_data/IDCKGEM000/rmm.phase.Last40days.gif)MJO phase diagram

**Download data:** [RMM Data](/clim_data/IDCKGEM000/rmm.74toRealtime.txt)

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

Methodology: Until the end of 2013 we use the exact method of Wheeler and Hendon (2004, [https://doi.org/10.1175/1520-0493(2004)132%3C1917:AARMMI%3E2.0.CO;2](https://doi.org/10.1175/1520-0493(2004)132%3C1917:AARMMI%3E2.0.CO;2)) and from 2014 we use the modified method of Gottschalck et al. (2010, [https://doi.org/10.1175/2010BAMS2816.1](https://doi.org/10.1175/2010BAMS2816.1)).


## 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](https://doi.org/10.1175/JCLI-D-22-0357.1).

These maps show average minimum or maximum temperature anomalies for each of the 8 MJO phases.
Red-yellow colours indicate higher than normal temperature,
while blue colours indicate lower than normal temperature.


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.


Outgoing longwave radiation (OLR) is often used as a way to identify tall, thick, convective rain clouds. These maps show the difference from expected cloudiness based on the position of the MJO. The violet and blue shading indicates higher than normal, active or enhanced tropical weather, while orange shading indicates lower than normal cloud or suppressed conditions.


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


These maps show the atmospheric troughs and ridges (in blue and red, respectively) associated with the different phases of the MJO at the 500hPa level. The 500 hPa level is approximately 5500 m above sea level and is about the middle of the troposphere. Colour shading is only used where the geopotential height anomalies are determined to be statistically-significant at the 5% level.


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


Wind RainfallOLRMax temperatureMin temperatureGeopotential Season
Jan–MarFeb–AprMar–MayApr–JunMay–JulJun–AugJul–SepAug–OctSep–NovOct–DecNov–JanDec–Feb

![](/clim_data/IDCKGEM000/mjo2oztemperature_tmax_JFM.png)

## 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 1 day3 days7 days1 month3 month6 month1 year Archive
Months
Jan–MarFeb–AprMar–MayApr–JunMay–JulJun–AugJul–SepAug–OctSep–NovOct–DecNov–JanDec–FebYear


![](/clim_data/IDCKGEM000/map_7.ps.png)Maps of total and anomaly outgoing longwave radiation (OLR)

## Regional timeseries charts of outgoing longwave radiation (OLR)

The charts linked from this map show the OLRs for the different regions within the Darwin RSMC area. The horizontal dashed line represents what is
normal for that time of year (based on the 1979 to 1998 period). The coloured
curve is the 3-day moving average
OLR in W/m². Below normal OLR indicates cloudier than normal conditions in this
particular area, and is shown in blue shading. Above normal OLR indicates less
cloudy conditions and is shown in yellow shading.


Tap boxes to view a timeseries chart of cloudiness for that regionimage/svg+xmlSouthern India and Sri LankaSouthern India and Sri LankaIndochinaIndochinaPhilippinesPhilippinesMalaysia and IndonesiaMalaysia and IndonesiaGuam and MarianasGuam and MarianasMicronesiaMicronesiaNorthern AustraliaNorthern AustraliaCoral SeaCoral SeaVanuatuVanuatuFijiFijiNew GuineaNew GuineaSolomon IslandsSolomon IslandsNauru and TuvaluDatelineDateline

## 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.


Latest 6 months Archive
Months
Jan–JunJul–DecYear


### Daily averaged OLR anomalies

![Daily averaged OLR anomalies](/clim_data/IDCKGEM000/olr_hovs_183_-15_15.ps.png)

### Westerly wind anomalies

![Westerly wind anomalies](/climate/mjo/graphics/winds_hovs_u850_183_-15_15.ps.png)

## History

- ### [Previous Climate Driver Updates](/climate/enso/wrap-up/archive.shtml)


Issued 3 September 2024

In the tropical Pacific Ocean, July sea surface temperatures (SSTs) were:

- up to 1.2 °C warmer than average across much of the western tropical Pacific Ocean, reaching up to 2 °C warmer than average for the far east
- up to 2 °C cooler than average in patches of the equatorial Pacific, east of 140°W, and parts of the South American coast.

In Australian coastal waters, July sea surface temperatures (SSTs) were:

- up to 2 °C warmer than average in waters surrounding most of Australia, and up to 3 °C warmer than average to the south-west of the mainland and south-east of Tasmania
- up to 2 °C cooler than average, along the South Australian coast extending to the western Tasmania coast, likely due to enhanced upwelling.

Around the Maritime Continent, July sea surface temperatures (SSTs) were:

- up to 1.2 °C warmer than average to the north of the Maritime Continent.

The Bureau's long-range forecast for September to November indicates SSTs are likely to be:

- up to 1.2 °C warmer than average in Australian coastal waters
- up to 2 °C warmer than average in the Tasman Sea and south of Tasmania
- up to 1.2 °C cooler than average in the central equatorial Pacific, between 170°W and 110°W; and up to 1.2 °C warmer than average for most of the western tropical and south-west Pacific.

For the week ending 1 September 2024, sea surface temperatures (SSTs) were:

- up to 2 °C warmer than the 1991–2020 average across much of the tropical Pacific Ocean west of 140°W, and reaching up to 4 °C warmer than average for the far eastern equatorial Pacific
- up to 2 °C cooler than average in parts of the eastern equatorial Pacific, between 150°W and 85°W
- 0.8–2 °C warmer than average around much of Australia's coastline, but warmer around south-west WA, the Gulf of Carpentaria and eastern Tasmania where temperatures were up to 3 °C above average
- close to average for coastal regions of the Great Australian Bite and parts of Bass Strait
- warmer than average across most of the Maritime Continent, by up to 1.2 °C, but for waters around north-east Papua New Guinea, temperatures were up to 2 °C above average.

The [Niño indices](http://www.bom.gov.au/climate/influences/images/map-indices.png) for the week ending 1 September 2024 are: Niño3, −0.24 °C; Niño3.4, −0.01 °C; and Niño4, +0.41 °C. These values reflect historically neutral ENSO conditions.

The 30–, 60– and 90-day Southern Oscillation Index (SOI) for the period ending 1 September were +8.3, −0.3 and −0.6 respectively. These values reflect ENSO-neutral conditions.

Trade wind strength for the 5 days ending 1 September was above average across the western and central tropical Pacific; elsewhere, the trade wind strength was close to average.

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

- A pulse of the Madden–Julian Oscillation (MJO) is currently in the Maritime Continent region to Australia's north (as at 1 September).
- Although ACCESS-S suggests the pulse will weaken, most international models suggest the pulse will either maintain its strength or strengthen slightly as the MJO progresses over the Maritime Continent in the coming week.
- When the MJO is in the Maritime Continent at this time of year, it may contribute towards strengthening trade winds, which can assist with La Niña development.

## Current state

- The Indian Ocean Dipole (IOD) is neutral. The IOD index for the week ending 1 September was +0.15 °C.
- Sea surface temperatures (SSTs) for the week ending 1 September 2024 were 0.8 to 2 °C warmer than the 1991–2020 average across much of Indian Ocean, but close to average in the parts of the tropical Indian ocean.
- Closer to Australia, SSTs were up to 2 °C warmer than average for waters surrounding WA.

## Forecast

- Most [climate models](http://www.bom.gov.au/climate/model-summary/#tabs=Indian-Ocean) indicate the IOD is likely to remain neutral until at least the end of spring.
- IOD forecast skill has historically been low at this time of year for forecasts beyond two months ahead.

Cloudiness near the equatorial Date Line is currently below average (as at 1 September). Cloudiness has been below average for most of August.

Equatorial cloudiness near the Date Line typically increases during El Niño (below average OLR) and decreases during La Niña (above average OLR).

The 4-month sequence of equatorial Pacific sub-surface temperature anomalies (to 29 August 2024) shows:

- sustained cool anomalies in the central and eastern Pacific during August, up to 2.5 °C below average between the 180°E and 80°W
- increased cool anomalies in the western Pacific during August, with waters cooling to 1.5 °C below average between depths of 125–300 m and longitudes of 130°E and 160°E
- warm anomalies in the top 100 m of the central and western equatorial Pacific (between 130°E and 180°E) strengthened slightly during August, reaching up to 2 °C warmer than average.

For the 5 days ending 1 September 2024:

- cool anomalies persisted at depths of 100 to 225 m in the central Pacific sub-surface where waters were 1 to 3 °C cooler than average, with the strongest anomalies at around 125 m depth east of the dateline
- warm anomalies up to 3 °C between the surface and 125 m persisted in the western Pacific and emerged in the eastern Pacific
- compared to the last fortnight, sub-surface waters have warmed in the eastern Pacific, and the extent of the cool anomalies has expanded in the western Pacific.

The El Niño–Southern Oscillation (ENSO) is currently neutral.

Sea surface temperatures (SSTs) in the central equatorial Pacific Ocean are ENSO-neutral, having gradually cooled from El Niño levels since December 2023. This cooling is being sustained by deep waters surfacing in the central and eastern Pacific. Atmospheric patterns, including cloud and trade winds, remain largely ENSO-neutral.

Three of 7 [climate models](http://www.bom.gov.au/climate/model-summary/#tabs=Pacific-Ocean&region=NINO34) suggest the possibility of SSTs in the tropical Pacific exceeding the La Niña threshold (below −0.8 °C) from October, while the remaining 4 models, including the Bureau's, suggest SSTs are likely to remain at ENSO-neutral values (between −0.8 °C to +0.8 °C ) throughout the forecast period. This means it is possible a La Niña may develop in coming months.

The Indian Ocean Dipole (IOD) is currently neutral, with the latest weekly IOD index value (as of 1 September) of +0.15 °C. Most models indicate that the IOD is likely to remain neutral until at least the end of spring.

Global SSTs were the warmest on record for each month between April 2023 and June 2024. July 2024 global SSTs were the second warmest on record, not as warm as July 2023 but much warmer than any other year. August 2024 is currently tracking as the second-warmest August for SSTs on record. The current global pattern of warmth differs to historical patterns of SSTs associated with ENSO and IOD. This means future predictions of ENSO and IOD based on SSTs during past events may not be reliable. Phenomena such as ENSO and the IOD are only broad indicators of the expected climate. The long-range forecast provides better guidance on local rainfall and temperature patterns.

The Southern Annular Mode (SAM) is currently positive (as at 1 September), having been neutral for most of the second half of August. The SAM index is forecast to become neutral during the coming week. A neutral SAM has no strong influence on Australian rainfall and temperature patterns.

A pulse of the Madden–Julian Oscillation (MJO) is currently in the Maritime Continent region to Australia's north (as at 1 September). Most models suggest the pulse will either maintain its strength or strengthen slightly as the MJO progresses over the Maritime Continent in the coming week. When the MJO is in the Maritime Continent at this time of year, it may contribute towards strengthening trade winds, which can assist with La Niña development.

- The Southern Annular Mode (SAM) is positive (as at 1 September), having been neutral for most of the second half of August.
- The SAM index is forecast to become neutral during the coming week.
- Predictability of the SAM beyond two weeks is typically low.
- A neutral SAM has no strong signal on long-range forecast conditions.

- ENSO is currently neutral.
- The Bureau's model indicates a neutral but cooler than average ENSO state. Of the remaining 6 [international models](http://www.bom.gov.au/climate/model-summary/#tabs=Pacific-Ocean&region=NINO34) surveyed by the Bureau, 3 indicate SSTs in the central tropical Pacific remaining within historically ENSO-neutral values (between −0.8 °C to +0.8 °C), and 3 indicate SSTs exceeding the La Niña threshold (below −0.8 °C) from October.
- Historically, the ENSO forecast skill is high at this time of year for up to 4 months ahead.

Product code: IDCKGEWW00

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Unless otherwise noted, all maps, graphs and diagrams in this page are licensed under the [Creative Commons Attribution 4.0 International Licence](https://creativecommons.org/licenses/by/4.0/)

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**on Wednesday 11 September 2024 (UTC)**

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