Climate Driver Update archive
Climate drivers in the Pacific, Indian and Southern oceans and the Tropics
Average of international model outlooks for NINO3.4
Average of international model outlooks for IOD
Sea surface temperature maps
Sea surface temperature maps are not available for forecasts before Spring 2018
SST outlooks for the next 3 months
ENSO is the oscillation between El Niño and La Niña states in the Pacific region. El Niños typically produce drier seasons, and La Niñas drive wetter years, but the influence of each event varies, particularly in conjunction with other climate influences.
International climate model outlooks
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
Southern Oscillation Index
Cloudiness near the Date Line
The Indian Ocean Dipole (IOD) compares sea surface temperatures. An IOD negative state, having warmer than average sea surface temperatures near Australia, provides more moisture for frontal systems and lows crossing Australia.
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.
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.
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.
Sea surface temperatures (SSTs) for the week ending 29 September remain warmer than average across the western to central equatorial Pacific Ocean, and slightly cooler than average in parts of the east, but overall patterns are consistent with a neutral ENSO state. Most of the northern half of the Pacific Ocean is warmer than average, as well as areas south of 30°S.
As well as cooler than average surface waters in areas along the eastern half of the equator, cool anomalies also extend through the east of the South Pacific close to South America. Surface waters between Australia and Papua New Guinea, across the Arafura Sea, and on the southern side of the Indonesian archipelago are also cooler than average. Cooler waters in this area of the eastern Indian Ocean typically occur during a positive IOD.
The latest values of the three key NINO indices in the tropical Pacific for the week ending 29 September are: NINO3 −0.1 °C, NINO3.4 +0.2 °C and NINO4 +0.8 °C. All three NINO indices have warmed compared to two weeks ago.
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.
In the tropical Pacific Ocean, the El Niño–Southern Oscillation (ENSO) remains neutral. The positive Indian Ocean Dipole (IOD) has strengthened, continuing its influence on the climate of Australia and other parts of the globe.
The very strong positive Indian Ocean Dipole event persists, characterised by cooler waters to the northwest of Australia and warmer waters further west. Values of the IOD index over the past fortnight have strengthened, and the latest value of +1.76 °C is the strongest positive weekly value since at least 2001.
All international climate models surveyed by the Bureau indicate the positive IOD is likely to persist at least until the end of the southern hemisphere spring. At the beginning of summer, the IOD pattern normally breaks down as the monsoon trough migrates into the southern hemisphere. Learn more about the Indian Ocean Dipole.
Typically, a positive IOD brings below average winter–spring rainfall to southern and central Australia, with warmer days for the southern two-thirds of the country. Positive IOD events are often associated with a more severe fire season for southeast Australia.
In the Pacific Ocean, the El Niño–Southern Oscillation (ENSO) remains neutral. Most atmospheric indicators are neutral, although the Southern Oscillation Index (SOI) is negative due to very high atmospheric pressures at Darwin. International climate models forecast neutral ENSO for the remainder of 2019, and into early 2020. When ENSO is neutral, it has little effect on Australian and global climate, meaning other influences are more likely to dominate.
Cloudiness near the Date Line has fluctuated around average values since late April, consistent with neutral ENSO. However, cloudiness near the Date Line has been moderately decreased for the last two thirds of September.
Equatorial cloudiness near the Date Line typically increases during El Niño (negative OLR anomalies) and decreases during La Niña (positive OLR anomalies).
Trade winds for the 5 days ending 29 September were close to average across the tropical Pacific.
During El Niño there is a sustained weakening, or even reversal, of the trade winds across much of the tropical Pacific. Conversely, during La Niña, there is a sustained strengthening of the trade winds.
All eight surveyed international climate models indicate central tropical Pacific sea surface temperatures in the NINO3.4 region will remain at ENSO-neutral levels until at least late 2019.
One model indicates that values may approach El Niño thresholds for December through February, while one other model shows cooling over the same period, and reaches the La Niña threshold in February. The remaining six models are all clearly predicting NINO3.4 values within the neutral range.
Sea surface temperatures (SSTs) for August were warmer than average across the western tropical Pacific Ocean, near-average for the central tropical Pacific, and cooler than average in some parts of the eastern equatorial Pacific, extending into the south Pacific close to South America.
SSTs were warmer than average to Australia's east, with this warmth extending across the Tasman Sea and well to the east of New Zealand, although anomalies were smaller than during July. SSTs were mostly close to average around the rest of Australia, though there were small areas of both cool and warm anomalies near the southwest of the continent.
The August values for NINO3 were 0.0 °C, NINO3.4 +0.2 °C, and NINO4 +0.7 °C. All three NINO indices cooled compared to July.
The 30-day Southern Oscillation Index (SOI) for the 30 days ending 29 September was −12.8. The 90-day value was −9.0. Recent negative SOI values are due to very high atmospheric pressure over Darwin.
Sustained negative values of the SOI below −7 typically indicate El Niño while sustained positive values above +7 typically indicate La Niña. Values between +7 and −7 generally indicate neutral conditions.
The Indian Ocean Dipole (IOD) remains positive, with the latest weekly index value to 29 September at +1.76 °C. This is the highest weekly value observed in the Bureau's dataset which extends from 2001 to present. Last week's value of +1.50 °C is the second highest on record.
The overall pattern of sea surface temperatures has remained generally consistent with a positive IOD pattern since late May, with warmer than average sea surface temperatures in the central and western tropical Indian Ocean, and average to cooler than average waters in the eastern tropical Indian Ocean, to the north of Australia and south of Indonesia.
All six international climate models surveyed by the Bureau indicate the IOD will remain positive into December. IOD events usually dissipate by early summer as the monsoon trough moves into the southern hemisphere, which changes the broadscale wind patterns over the IOD region and returns sea surface temperatures to near average. Models are indicating a slower break down of the IOD than usual, but it remains unlikely that the positive IOD influence will persist far into summer.
A positive IOD often results in below average winter–spring rainfall over southern and central Australia. It also typically means warmer than average winter–spring days for the southern two-thirds of Australia.
The four-month sequence of equatorial sub-surface temperature anomalies (to 28 September) shows a pattern of weak cool anomalies extending across the equatorial Pacific, at a depth of around 100 to 200 m in the west of the Basin, and 0 to 150 m depth in the east. Weak warm anomalies extend across most of the column depth between about 160°E and 160°W. This general pattern has been in place since July.
Cool anomalies in the east have intensified in September and reach more than 3 degrees cooler than average, while warm anomalies in the west are weaker, reaching up to 2 degrees warmer than average.
For the five days ending 29 September water temperatures were close to average across much of the sub-surface of the equatorial Pacific. However, there was a volume of cooler than average water in the east centred around 120°W and 100 m depth, with anomalies reaching more than 2 degrees cooler than average in a small region, and a volume of weaker warm anomalies in the west centred around 100 to 150 m depth near the Date Line, with anomalies reaching more than 2 degrees warmer than average.
The strength of the cool anomalies in the east has decreased compared to two weeks ago.
Product code: IDCKGEWW00