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 along the equator in the Pacific Ocean, across much of the tropics to the north of the equator, and much of the western Pacific both north and south of the equator. SSTs within the NINO3 and NINO3.4 region are now both above the El Niño threshold.

The latest values of the key NINO indices in the tropical Pacific for the week ending 4 November are: NINO3 +0.9 °C, NINO3.4 +0.9 °C and NINO4 +0.9 °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 along much of the east coast, with very weak warm anomalies extending across much of the Bight and parts of the northern coastline.

The tropical Pacific Ocean continues developing towards El Niño, while in the Indian Ocean, a positive Indian Ocean Dipole (IOD) is underway. The Bureau's ENSO Outlook remains at El Niño ALERT, meaning there is approximately a 70% chance of El Niño occurring in the coming months; about triple the normal likelihood.

Ocean temperature patterns in the Indian Ocean have been at positive IOD levels now for two months. As a result, 2018 will be considered a positive IOD year. A positive IOD during spring increases the chance of below average rainfall for southern and central Australia, and can reinforce the effects of a developing, or fully formed, El Niño. El Niño effects in Australia over summer include higher fire risk, greater chance of heatwaves, and fewer tropical cyclones.

Sea surface temperatures in the tropical Pacific Ocean have warmed to El Niño levels over the past fortnight. However, atmospheric indicators of El Niño are largely near normal, suggesting that the ocean and atmosphere are not yet reinforcing each other, or 'coupled'. This reinforcement is critical in any El Niño developing and becoming self-sustaining.

International climate models suggest further warming of the tropical Pacific Ocean is likely, increasing the possibility of coupling occurring in the coming months. Seven out of eight climate models suggests sea surface temperatures will remain above El Niño thresholds until at least March 2019.

Model outlooks suggest the positive IOD will decay during November. IOD events typically have little influence on Australian climate from December to April.

Cloudiness near the Date Line has generally remained below average (positive OLR anomalies) since mid-September. 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 4 November were close to average across the tropical Pacific. This continues to suggest that the atmosphere and ocean are not yet reinforcing each other, which is required for an event to become firmly established.

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 surveyed models predict the tropical Pacific Ocean will continue to warm in the coming months. All but one of the surveyed climate models predict central equatorial Pacific sea surface temperatures (SSTs) will exceed El Niño thresholds until at least March 2019.

El Niño onset during November or December would be later than usual, although not unprecedented.

 

Sea surface temperature (SST) for October were warmer than average across the equatorial Pacific Ocean, and much of the tropics north of the equator, and much of the western Pacific both north and south of the equator.

The October values for NINO3 were +0.8 °C, NINO3.4 +0.8 °C, and NINO4 +0.9 °C. NINO3 and NINO3.4 have both warmed by half a degree compared to September.

The 30-day Southern Oscillation Index (SOI) to 5 November was +3.0, and the 90-day SOI was −4.3. The SOI has remained within the neutral ENSO range for the past four weeks. The lack of a clear signal in the SOI indicates that the atmospheric circulation required to signal the start of an El Niño event, and to reinforce and sustain an El Niño, is not yet present.

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.

A positive Indian Ocean Dipole (IOD) has been underway since early September. The latest weekly index value to 4 November was +0.38 °C. It is likely that this event is near its end, and that values will decline over the coming weeks, as is typical of the usual IOD seasonal cycle.

All of the six international climate models surveyed by the Bureau indicate that the positive IOD event will breakdown during November; this would be in line with the typical seasonal pattern of the IOD. 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.

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

The four-month sequence of sub-surface temperature anomalies (to October) shows warm anomalies in the sub-surface have increased significantly compared to the preceding months. A large pool of warmer than average water extends across the sub-surface of the equatorial Pacific, between about 150°E to about 100°W. Parts of this region are more than 3 degrees warmer than average.

Temperatures for the five days ending 4 November show warmer than average waters in the top 150 m of the sub-surface of the equatorial Pacific. A large volume of the sub-surface is more than 3 degrees warmer than average, with waters in part of the eastern equatorial Pacific sub-surface more than 4 degrees warmer than average.

Warm anomalies have continued to strengthen and progress eastward over the past two weeks. The eastward shift of anomalously warm water is a typical precursor of El Niño.

Product code: IDCKGEWW00