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

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.

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.

MJO phase diagram
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.

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 region
image/svg+xml Southern India and Sri Lanka Southern India and Sri Lanka Indochina Indochina Philippines Philippines Malaysia and Indonesia Malaysia and Indonesia Guam and Marianas Guam and Marianas Micronesia Micronesia Northern Australia Northern Australia Coral Sea Coral Sea Vanuatu Vanuatu Fiji Fiji New Guinea New Guinea Solomon Islands Solomon Islands Nauru and Tuvalu Dateline Dateline

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

Westerly wind anomalies

Sea surface temperatures (SSTs) for November 2023 were warmer than average across almost all the equatorial Pacific Ocean. Across much of the tropical Pacific between 10°S and 10°N, SST anomalies were more than 0.8 °C warmer than the long-term (1961–1990) average, increasing to up to 3 °C warmer than the long-term average east of the Date Line.

The extent of warm anomalies across the equatorial Pacific has slightly decreased compared to October.

Cool anomalies off the west coast of Java, Indonesia have also decreased in magnitude compared to October.

Warm SST anomalies also continued in the western Tasman Sea, including off most of the south-eastern coast of Australia, and have strengthened across other parts of the Tasman Sea. Warm anomalies to the west of Australia decreased in magnitude compared to October, with waters warmer than 0.8 °C above average surrounding much of Western Australia.

The Bureau's long-range forecasts indicate warmer than average SSTs (up to around 2 °C warmer than average) off the coast of south-east Australia will likely continue through the southern hemisphere summer 2023–24. Forecast unusually warm sea surface temperatures (SSTs) in the Tasman Sea may also be contributing to a chance of above median summer rainfall over parts of Australia. Warm anomalies in the Coral Sea are forecast to persist into early 2024.

Globally, in the ERSSTv5 dataset, SSTs for April to November 2023 were warmest on record (since 1900) for their respective months. August and September SSTs were also globally warmest and second-warmest, respectively, for any month.

For the week ending 3 December 2023, sea surface temperatures (SSTs) were warmer than average across the equatorial region of the tropical Pacific Ocean. Anomalies were more than 1.2 °C warmer than average east of the Date Line, excluding regions along the Peruvian coast south of the equator, which have cooled to 0.8 °C warmer than average. Anomalies were more than 2 °C warmer than average in some areas of the central and eastern tropical Pacific. Compared to last fortnight, warm anomalies have generally decreased, particularly along the equator and the far eastern Pacific.

Closer to Australia, warm anomalies up to 3 °C above average persist off the south-east coast, with anomalies up to 2 °C above average extending into the southern Tasman Sea. There were also warm SST anomalies off the north-west and south-west coasts of Australia, mostly up to about 1.2 °C above average. Compared to last fortnight, warm anomalies have returned to the Coral Sea and the warm anomalies in the Tasman Sea have slightly increased.

The latest values of the three NINO indices for the week ending 3 December 2023 were: NINO3, +1.69 °C; NINO3.4, +1.77 °C; and NINO4, +1.60 °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 3 December 2023 were −8.1, −7.2 and −9.1, respectively.

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

Trade winds for the 5 days ending 3 December 2023 were close to average over the equatorial Pacific.

Trade winds for November 2023 have been slightly weaker to weaker than average across the western equatorial Pacific. Trade winds were stronger than average over the central and western Pacific during the second half of November. Trade winds have been weaker than average over the central equatorial Pacific for most of September to November.

During El Niño, there is typically 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.

A moderate to strong pulse of the Madden–Julian Oscillation (MJO) is currently over the Maritime Continent. International climate models suggest it will move across the Maritime Continent and into the western Pacific over the coming fortnight. This would typically have a wetting influence on parts of northern and central Australia.

The positive Indian Ocean Dipole (IOD) event continues. The IOD index is +1.20 °C for the week ending 3 December 2023. The weekly IOD index values for this event have been the second-highest on record since the Bureau SST dataset began in 2001, with the highest on record being during the strong positive IOD event of 2019. To date, the highest weekly IOD index for the current event was +1.92 °C for the week ending 15 October.

Sea surface temperatures (SSTs) for the week ending 3 December show warmer than average waters across much of the western half of the tropical Indian Ocean and south of 15°S. Conversely, the eastern pole of the IOD was cooler than average, with a small area of cooler waters extending off the coast of Java, Indonesia. A gradient between the western and eastern tropical Indian Ocean that is typical of a positive IOD is still apparent but compared to last fortnight, the strength and extent of the cooling in the eastern pole has reduced and there has been a slight decrease in the strength of the anomalous warmth in the western pole.

IOD events typically breakdown as the monsoon trough shifts south into the southern hemisphere, typically at the end of spring. Given the current strength of this event and the active El Niño, the breakdown this year is likely to be slightly later than usual. All international climate models surveyed by the Bureau suggest the positive IOD event is likely to ease in December.

December rainfall is likely to be below median for much of northern Australia, southern WA and along the coast in SA. When the positive IOD persists into December, the usual dry and warm signal associated with spring tends to persist as well, though typically to a lesser degree. However, the small number of years where the IOD has persisted into December means there is greater uncertainty on its typical impacts.

Outgoing Longwave Radiation (OLR) around the equatorial Date Line is currently below average (indicating increased cloudiness). OLR has been mostly below average since mid-September 2023. 

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 30 November 2023) shows warm anomalies across most of the top 100 m of the equatorial Pacific band, with the exception of the western Pacific. Anomalies increase in magnitude eastwards across the equatorial Pacific band with the central Pacific up to 2.5 °C warmer than average, and the eastern Pacific more than 2.5 °C warmer than average.

Warm anomalies have persisted in the central and eastern Pacific between the surface and 200 m depth. Compared to September, the depth of warm anomalies above 1 °C in the central Pacific have increased to depths of 200 m. The depth of warm anomalies in the eastern Pacific has decreased over the past 4 months. West of the Date Line, cool anomalies continue to strengthen between 100 and 300 m depth, undercutting warm anomalies above them in the central Pacific.

For the 5 days ending 3 December 2023, sub-surface temperatures were warmer than average across the upper levels of the equatorial Pacific east of the Date Line, between the surface to around 100 m depth in the eastern Pacific and between the surface to around 180 m depth in the central Pacific. Much of this region was more than 2 °C warmer than average, with anomalies more than 5 °C warmer than average between 125 °W and 95 °W at around 50 m depth.

Compared to last fortnight, the magnitude of warm anomalies in the central Pacific have increased. Cool anomalies have increased in magnitude and extent between 100 to 250 m below the surface in areas west of the Date Line.

The long-range forecast for Australia indicates December to February rainfall is likely to be below median across much of northern and western Australia. Warmer days and nights are very likely for almost all of Australia.

El Niño continues in the tropical Pacific. Indicators of the El Niño–Southern Oscillation (ENSO), including tropical Pacific sea surface temperatures (SSTs), cloud, wind, and pressure patterns are consistent with El Niño conditions. Climate model forecasts indicate some further warming of central to eastern Pacific SSTs is possible, with SSTs remaining above El Niño thresholds early into the second quarter of 2024.

The influence of El Niño on Australian rainfall usually reduces during summer, especially in the east; however, below median rainfall is still often observed in north-east Australia. Additionally, high-impact rainfall events can occur during El Niño years, particularly during October to April when severe storm frequency peaks.

The positive Indian Ocean Dipole (IOD) event continues. IOD index values have eased from their highest values in October and are unlikely to re-strengthen, meaning the positive IOD event is likely past its peak. All international climate models surveyed by the Bureau suggest the positive IOD is likely to ease in December.

The Southern Annular Mode (SAM) index is currently neutral. Forecasts suggest it is likely to remain mostly neutral over the coming fortnight. A neutral SAM has limited influence on Australian climate.

A moderate to strong Madden–Julian Oscillation (MJO) pulse is currently over the Maritime Continent. International climate models suggest it will move across the Maritime Continent and into the western Pacific over the coming fortnight. When the MJO is over the Maritime Continent, it typically increases rainfall over parts of northern and central Australia.

Global warming continues to influence Australian and global climate. Global sea surface temperatures (SSTs) were highest on record for their respective months during April to November. Forecast unusually warm sea surface temperatures (SSTs) in the Tasman Sea may also be contributing to a chance of above median summer rainfall over parts of Australia.

Australia's climate has warmed by 1.48 ± 0.23 °C since national records began in 1910. There has been an increase in extreme heat and fire weather associated with the warming. There has also been a trend towards a greater proportion of rainfall from high intensity, short duration rainfall events, especially across northern Australia.

The Bureau's climate model includes all influences on Australian climate when generating its forecasts, including the influence of climate change.

The Southern Annular Mode (SAM) is currently neutral. Forecasts indicate it is likely to remain mostly neutral for the coming fortnight. A neutral SAM has limited influence on Australian climate.

International climate models suggest some further warming of the central to eastern tropical Pacific Ocean is possible. All surveyed models indicate SSTs will remain above El Niño thresholds early into the second quarter of 2024. The 2023 El Niño event is tracking around at least moderate strength.

The long-range forecast for southern hemisphere summer (December to February) indicates rainfall is likely to be below median across much of northern and western Australia. This is consistent with historical patterns of reduced summer rainfall associated with El Niño, which typically show a drier summer for north-east Australia. The influence of El Niño on Australian rainfall usually reduces during summer, especially in the east; however, below median rainfall is still often observed in north-east Australia. Additionally, high-impact rainfall events can occur during El Niño years, particularly during October to April when severe storm frequency peaks.

Product code: IDCKGEWW00

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