ENSO Wrap-Up
Current state of the Pacific and Indian oceans


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

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ENSO outlooks

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.

Indian Ocean Dipole outlooks

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.

Sea surface temperatures (SSTs) are warmer than average across the central and eastern tropical Pacific Ocean, as is typical for an El Niño event. However, SSTs are also warmer than average over large parts of the western Pacific, and in a broad band across the southern Pacific extending from the tropics in the west to around 30°S in the east; the opposite of what is expected in a typical El Niño.

SSTs within both the NINO3 and NINO3.4 region have cooled slightly compared to two weeks ago, but have remained just above the El Niño threshold for the past eight weeks. The latest values of the key NINO indices in the tropical Pacific for the week ending 16 December are: NINO3 +0.8 °C, NINO3.4 +0.8 °C and NINO4 +1.0 °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.

Around Australia, SSTs are warmer than average across the northern Coral Sea and parts of the Torres Strait, and also around southeastern Australia from the eastern side of the Great Australian Bight, up the New South Wales coast, and across the Tasman Sea. SSTs in the Tasman Sea are more than one degree warmer than average.

In the Gulf of Carpentaria, previously warmer than average SSTs have eased back to near average with the passing of severe tropical cyclone Owen. Cool anomalies are present off the western coast of Australia, associated with a weaker than average Leeuwin Current.

The El Niño–Southern Oscillation (ENSO) remains neutral, despite ocean temperatures being at El Niño levels. The Bureau's ENSO Outlook remains at El Niño ALERT.

The term El Niño–Southern Oscillation refers to the interaction between the tropical Pacific Ocean ("El Niño") and its overlying atmosphere ("Southern Oscillation"), which together produce a global influence on weather and climate. While tropical Pacific sea surface temperatures (SSTs) are currently at El Niño levels, atmospheric indicators—such as cloudiness, pressure patterns, the Southern Oscillation Index (SOI) and trade winds—have generally remained neutral.

This means that the ocean and atmosphere are not reinforcing each other, known as coupling. It is this coupling that defines and sustains an ENSO event, and results in widespread shifts in global weather and climate.

The natural seasonal cycle of tropical Pacific SSTs and cloud means that the likelihood of an ENSO event developing during mid-summer is lower than at other times of year. This is because the difference in SSTs across the Pacific Basin eases towards a minimum in late summer to autumn. Late developing El Niño events do occur, such as in 2006–07 and 2009–10, although there is no record of one starting in January.

Most models indicate SSTs in the tropical Pacific Ocean are likely to remain near or above El Niño levels until at least the middle of 2019. However, models typically have less skill when forecasting through autumn. If SSTs did maintain their current anomalous warmth through summer, it would increase the chance of El Niño emerging in 2019.

The positive Indian Ocean Dipole (IOD) event has ended, and neutral IOD conditions prevail. The IOD typically has little influence on Australian climate from December to April.

Cloudiness near the Date Line has fluctuated around average since late October, whereas typically it would be well above average during El Niño.

In addition to cloudiness near the Date Line, the broader cloud pattern across the tropical Pacific is more typical of a neutral ENSO state. Again, this indicates that coupling of the ocean and atmosphere has yet to occur.

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 five days ending 16 December were mixed, with weaker than average trades across the far western equatorial Pacific, but stronger than average trades near the Date Line. Weaker-than-average trade winds have appeared at times during the past month to two months, but have been associated with transient events, such as pulses of the Madden–Julian Oscillation.

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.

The lack, so far, of this sustained pattern is one of the indicators that the atmosphere and ocean are not yet reinforcing each other, which is required for an event to become firmly established.

Five of the eight surveyed climate models predict sea surface temperatures (SSTs) will remain above El Niño thresholds well into the southern hemisphere autumn of 2019. The other three models remain warmer than average, but do not exceed El Niño thresholds.

While the models indicate elevated sea surface temperatures in the tropical Pacific will persist, El Niño onset during summer would be unusual. The seasonal cycle typically favours a decay of gradients in SSTs across the tropical Pacific during summer to autumn, as this is the time of year when the tropical Pacific Ocean naturally evens out the temperature difference between the east and west.

Sea surface temperatures (SSTs) for November were warmer than average along the equator and much of the tropical Pacific Ocean, and much of the southern Pacific.

The November values for NINO3 were +0.9 °C, NINO3.4 +0.9 °C, and NINO4 +0.9 °C.

The 30-day Southern Oscillation Index (SOI) to 16 December was +7.9, and the 90-day SOI was +1.0. The SOI has remained within the neutral ENSO range since early September, when it briefly reached El Niño thresholds.

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 lack of a clear, sustained El Niño signal in the SOI is one indicator (see also Trade Winds and Cloudiness) that the atmospheric circulation required to signal the start of El Niño has not established. This atmospheric coupling is the mechanism which reinforces and sustains El Niño, and facilitates widespread shifts in Australian and global weather and climate.

The Indian Ocean Dipole (IOD) is currently neutral, following the conclusion of the positive IOD event at the start of December. The latest weekly index value to 16 December was +0.28 °C.

Due to the movement of the monsoon trough in the Indian Ocean, the IOD typically has little influence on Australian climate from December to April. When the monsoon trough shifts southwards into the southern hemisphere, it changes the broadscale wind patterns, meaning that the IOD pattern is unable to form.

All of the six international climate models surveyed by the Bureau indicate that the IOD will remain neutral into autumn 2019.

 

The four-month sequence of sub-surface temperature anomalies (to November) shows warm anomalies in the sub-surface have progressed eastward over recent months. A large pool of warmer than average water extends across the sub-surface of the equatorial Pacific, between about 150°E and the eastern edge of the Pacific Basin. Small parts of the sub-surface in the eastern equatorial Pacific were more than three degrees warmer than average.

Temperatures for the five days ending 16 December show warmer than average waters in the top 100–200 m of the sub-surface of the equatorial Pacific. A volume of water in the the sub-surface of the central equatorial Pacific is more than four degrees warmer than average, with waters closer to the surface in the eastern Pacific more than three degrees warmer than average.

Waters in the sub-surface of the central equatorial Pacific have warmed compared to two weeks ago, while warm anomalies have continued to progress towards the eastern equatorial Pacific sub-surface. This eastward shift of anomalously warm water is a typical precursor of El Niño.

Product code: IDCKGEWW00