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 POAMA forecasts, updated daily
Select to see full-size map of NINIO3.4 SST plumes from POAMA forecasts, updated daily.

Indian Ocean Dipole outlooks

IOD SST plumes from POAMA forecasts, updated daily
Select to see full-size map of IOD SST plumes from POAMA forecasts, updated daily.

Sea surface temperatures (SSTs) in the central tropical Pacific Ocean are within the ENSO-neutral range, but remain slightly cooler than average along most of the central equatorial Pacific. Cool anomalies between the Date Line and 150° W have strengthened over the past two weeks. SSTs in the NINO3.4 region were 0.62 °C cooler than average for the week ending 9 October.

SSTs in the western Pacific and across South East Asia, including areas around northern Australia and across the Tasman Sea, remain warmer than average, and exceed 1 °C warmer than average in some areas.

Warm SST anomalies also persist in the eastern Indian Ocean between the northwest of Australia and Indonesia, while areas of cool anomalies are present in the western Indian Ocean around the Horn of Africa, consistent with the persistent negative Indian Ocean Dipole (IOD) event. However, anomalies in the western Indian Ocean have warmed in the past fortnight, weakening the overall negative IOD value. South of Indonesia waters remain at least 1 °C warmer than average, with some coastal areas more than 2 °C warmer than average.

The tropical Pacific Ocean remains El Niño–Southern Oscillation (ENSO) neutral, however, some indicators have shifted closer to La Niña thresholds. Conversely, the negative Indian Ocean Dipole (IOD) has eased, though waters off Indonesia remain at near record temperatures. This may see continued IOD impacts for Australia.

Sea surface temperatures (SSTs) in the tropical Pacific Ocean have cooled over the past fortnight, consistent with a surge in the trade winds. The latest weekly NINO3.4 value of −0.6 °C—while still at neutral levels—is a value not seen since February 2012 (the end of the 2010–12 La Niña). Cloudiness near the Date Line and the Southern Oscillation Index have also shifted closer to La Niña-like levels. However, some forecasts suggest trade winds may return to near-normal soon. This could occur with the passage of the Madden–Julian Oscillation and would slow or cease any further La Niña development.

The majority of international climate models indicate the tropical Pacific is likely to remain at ENSO neutral levels through to the end of the 2016–17 summer. Two of the eight models suggest brief, weak La Niña levels are possible towards the end of 2016. The ENSO Outlook remains at La Niña WATCH.

With warmer than average sea surface temperatures to Australia's north and east, some La Niña-like impacts remain likely even if an event doesn't fully develop.

Negative IOD values have eased over the past fortnight, however this is mainly due to ocean warming off Africa. Waters off Indonesia remain very warm, and were second warmest on record for September. Models indicate the IOD will return to neutral levels by the end of spring. Spring in eastern Australia is typically wetter than average during a negative IOD or La Niña.

Cloudiness near the Date Line has been generally below average since the start of August.

Equatorial cloudiness near the Date Line typically increases during El Niño (below average OLR) and decreases during La Niña (above average OLR).

Trade winds in the western tropical Pacific Ocean were slightly stronger than average (i.e. +2 to +3 m/s) for the 5 days ending 9 October. Until recently, trade winds had generally remained close to average since March.

During La Niña events, there is a sustained strengthening of the trade winds across much of the tropical Pacific, while during El Niño events there is a sustained weakening, or even reversal, of the trade winds.

Outlooks from the eight international climate models surveyed by the Bureau continue to indicate that neutral ENSO conditions are the most likely outcome for the southern hemisphere spring–summer period.

However, two models indicate that a late-starting La Niña is possible, although only one sees the event persist throughout summer. Most models continue to include ensemble members which exceed La Niña thresholds for at least a short period.

If La Niña does form, models suggest it will be weak, potentially short-lived, and well below the strength of the significant 2010–12 event.

Weak cool SST anomalies persisted in a small region of the equatorial central Pacific during September. Warm anomalies have replaced cool anomalies along the equator in the eastern Pacific since August. September SSTs were warmer than average both north and south of the equator across most of the tropical Pacific, and across a large area of the tropical to temperate western Pacific south of the equator. Waters are also warmer than average around Australia, Indonesia and South East Asia. Large areas adjacent to southeast Australia and between Australia and Indonesia were more than 1 °C warmer than average.

The September value for the NINO3 region was −0.1 °C, 0.3 °C warmer than for August, while the value for the NINO3.4 region remained unchanged at −0.4 °C, and NINO4 was 0.2 °C cooler 0.0 °C. The eastern node of the IOD was second-warmest on record for September in the ERSSTv4 dataset.

The latest 30-day Southern Oscillation Index (SOI) to 9 October is +12.6, exceeding the La Niña threshold by +5.6. SOI values have been above the threshold for the past four weeks, though are expected to decline somewhat over the next fortnight as very high daily values are lost from the 30-day average.

Sustained positive values of the SOI above +7 typically indicate La Niña while sustained negative values below −7 typically indicate El Niño. Values between about +7 and −7 generally indicate neutral conditions.

The negative Indian Ocean Dipole (IOD) event continues, although it has declined in strength over the past fortnight. The weekly index value to 9 October was −0.38 °C.

This is the first week since the latter part of May that the IOD index value has been outside the −0.4 °C negative IOD threshold. However, the eastern node of the IOD was second-warmest on record for September in the ERSSTv4 dataset, coming in just behind the exceptional value of September 2010.

International climate models indicate the negative IOD will steadily weaken during spring, as is typical of the lifecycle of IOD events. This means its influence on Australian rainfall may lessen in the coming months.

A negative IOD typically brings above average rainfall to eastern Australia during spring, cooler than normal daytime temperatures to southern Australia, and warmer daytime and night-time temperatures to northern Australia.



The four-month sequence of sub-surface temperature anomalies (to September) shows cool anomalies span the entire width of the equatorial Pacific Ocean, although temperatures in the top 50 m of water west of 170° W have been slightly warmer than average in each month (June to September). Compared to August, warm anomalies in the western equatorial Pacific below 200 m depth have also strengthened during September, although remaining weak.

The sub-surface temperature map for the 5 days ending 9 October shows temperatures generally close to average across the sub-surface of the equatorial Pacific. Cool anomalies in the central region have weakened compared to two weeks ago. A few small areas of cool anomalies in excess of 2 degrees cooler than average were present in the far western and central regions.

Product code: IDCKGEWW00