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 parts of the central equatorial Pacific.

SSTs in the western Pacific, including around Australia's northern and eastern seaboard and across South East Asia, remain warmer than average, exceeding 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.

A persistent and strong negative phase of the Indian Ocean Dipole (IOD), combined with a La Niña-like pattern of warm seas around northern Australia, continue to be the major drivers of Australian climate.  

Temperatures in the central tropical Pacific Ocean continue to be below average, but remain El Niño–Southern Oscillation (ENSO) neutral. Most international climate models surveyed indicate the Pacific is likely to remain at ENSO neutral levels through to the end of 2016, though one international model suggests a La Niña late in the year is possible.

Some indications of atmospheric coupling have emerged in recent weeks. August was the first month to show persistent below average cloud around the Date Line (typical of La Niña), and this pattern has continued during September. Likewise, the Southern Oscillation Index has exceeded La Niña thresholds for the past two weeks. Hence the ENSO Outlook remains at La Niña WATCH.

Warmer than normal sea surface temperatures to Australia's north and east, and the broader southwest Pacific Ocean, strengthened over the past fortnight and may be contributing to some La Niña-like impacts. Likewise, a very strong negative IOD persists in the Indian Ocean and is also increasing the likelihood of wet conditions over Australia. 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 (and La Niña).

Cloudiness near the Date Line has been generally below average since the start of August, with values the lowest observed since 2013. However some locations in the western tropical Pacific have continued to see enhanced cloudiness; the opposite of what may be expected in La Niña years.

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

Trade winds along and to the north of the equator in the far western Pacific Ocean were slightly stronger than average for the 5 days ending 25 September. Trade winds have 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, one model continues to provide firm predictions of a late-starting La Niña and two other models predict borderline cool conditions are likely. Most models 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 SSTs anomalies persisted in a narrow band along much of the equator in the eastern and central Pacific during August, having decreased in strength compared to July. August SSTs were warmer than average both north and south of the equator in the eastern half of the tropical Pacific, and across most of the western half of the tropical Pacific, around Australia, and extending to Indonesia and South East Asia. Large areas around Australia's east coast and between Australia and Indonesia were more than 1 °C warmer than average.

The August value for the NINO3.4 region was −0.4 °C, 0.1 °C cooler than for July, while the value for the NINO4 region was 0.1 °C warmer at −0.2 °C, and NINO3 remained unchanged at −0.3 °C.

The latest 30-day Southern Oscillation Index (SOI) to 25 September 2016 is +13.1, above the La Niña threshold. SOI values have been above this threshold for the past two weeks, potentially indicating some enhanced coupling is occurring between the ocean and the atmosphere. 30-day SOI values had not previously exceeded the threshold value this year.

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, and remains very strong although index strength has dropped back from values earlier in September. The weekly index value to 25 September was −0.90 °C.

The Indian Ocean Dipole (IOD) index has been below the −0.4 °C negative IOD threshold for eighteen weeks, peaking at −1.37 °C in early July. The July 2016 monthly IOD index value reported in the ERSSTv4 dataset was the strongest negative value in at least 50 years of record.  

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 22 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 25 September shows temperatures generally close to average across the sub-surface of the equatorial Pacific, although cool anomalies in the central region have strengthened compared to two weeks ago. An area of cool anomalies in excess of 3 degrees cooler than average is now present between 155° W and 130° W, at 100 m to 150 m depth.

Product code: IDCKGEWW00