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 much of the tropical Pacific Ocean. SSTs are also warmer than average across much 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 latter is the opposite of what is expected from a typical El Niño SST pattern.

SSTs within both the NINO3 and NINO3.4 region have been above the El Niño threshold for the past six weeks. The latest values of the key NINO indices in the tropical Pacific for the week ending 2 December are: NINO3 +0.9 °C, NINO3.4 +0.9 °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 around much of the north, east and southeast coast, with weak warm anomalies extending from around the Top End, along much of the east coast, and across Bass Straight and the Tasman Sea. Further from Australia, surface temperatures in much of the Tasman Sea are more than one degree warmer than average. Cool anomalies are present off the western coast of Australia.

The tropical Pacific Ocean remains ENSO-neutral, despite some indicators reaching El Niño levels. As a result, the Bureau's ENSO Outlook remains at El Niño ALERT. The positive Indian Ocean Dipole (IOD) event in the tropical Indian Ocean weakened in the past fortnight.

Sea surface temperatures in the tropical Pacific Ocean have now exceeded El Niño thresholds for more than a month. However atmospheric indicators—such as trade winds, cloud patterns, and the Southern Oscillation Index (SOI)—have not reached El Niño levels. This indicates that the tropical ocean and atmosphere are not reinforcing each other and remain 'uncoupled'. This coupling is required to establish and sustain any ENSO event, and is what drives widespread Australian and global impacts.

Recently, trade winds in the western Pacific have weakened in association with the Madden–Julian Oscillation. Some models suggest they may remain weakened for at least the next fortnight.

International climate models predict sea surface temperatures to remain at or above El Niño levels in December and January. By February, all but one of the eight surveyed models remain above El Niño thresholds. El Niño effects in Australia over summer typically include higher fire risk, greater chance of heatwaves, and fewer tropical cyclones.

The positive IOD event which began in early September has weakened, with the most recent value just below positive thresholds. It is likely that the positive IOD is nearing its end—consistent with model outlooks and the IOD's natural cycle. The IOD typically has little influence on Australian climate from December to April.

Cloudiness near the Date Line has fluctuated to either side of average value during the last month and a half.

While decreased cloudiness near the Date Line is typically a signal seen during La Niña, the broader pattern across the tropical Pacific is consistent with neutral ENSO. 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 2 December were weaker than average across the western and central tropical Pacific, with the strongest anomalies evident on the northern side of the equator between the Date Line and the central Pacific. Weaker-than-normal trade winds have appeared at times during the past month, but have been associated with transient events, such as pulses of the Madden–Julian Oscillation. It remains to be seen whether this weakening of the trade winds will persist, or have a lasting effect.

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.

All surveyed climate models predict sea surface temperatures (SSTs) across the central tropical Pacific Ocean will be above El Niño thresholds during December. El Niño onset during December would be later than usual.

One model indicates SSTs will drop below El Niño thresholds in January. Nevertheless, five of the eight models maintain values consistent with El Niño throughout the southern hemisphere autumn. 

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 2 December was +1.6, and the 90-day SOI was −2.2. 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 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 Australian and global weather impacts.

A positive Indian Ocean Dipole (IOD) has been underway since early September. The latest weekly index value to 2 December was +0.34 °C, just below the threshold value of +0.40 °C. Given the time of the year, it is likely that values will decline further over the coming weeks and draw the event to an end.

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.

Four of the six international climate models surveyed by the Bureau indicate that the positive IOD event will breakdown during December.

A positive IOD event typically reduces spring rainfall over much of northern, central and southern Australia, and can exacerbate any potential El Niño-driven rainfall deficiencies.

 

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 2 December show warmer than average waters in the top 100–200 m of the sub-surface of the equatorial Pacific. A large volume of the sub-surface is more than three degrees warmer than average, with waters in part of the shallow eastern Pacific sub-surface more than four degrees warmer than average.

Waters in the sub-surface around the Date Line have warmed compared to two weeks ago, while warm anomalies have decreased and contracted eastward in the eastern equatorial Pacific sub-surface. The eastward shift of anomalously warm water is a typical precursor of El Niño.

Product code: IDCKGEWW00