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.

Compared to two weeks ago, warm SST anomalies have strengthened in the eastern Indian Ocean between the northwest of Australia and Indonesia. Areas of weak cool anomalies have also re-emerged in the western Indian Ocean off Africa, corresponding to a strengthening of the negative Indian Ocean Dipole (IOD) event.

A new surge in strength of the negative Indian Ocean Dipole (IOD), combined with a La Niña–like pattern in the tropical Pacific Ocean and seas around Australia, is strongly influencing Australian climate.

In the Indian Ocean, the negative IOD has strengthened, after easing somewhat during August. The weekly IOD index is close to the record values observed in July. Despite this recent re-intensification, climate models continue to suggest the IOD will weaken in the coming months, returning to neutral values before the end of 2016. During a negative IOD much of eastern Australia typically experiences above average spring rainfall.

In the Pacific Ocean, although some La Niña–like patterns are present, there remains limited connection between the atmosphere and ocean, and hence La Niña thresholds are yet to be met. A La Niña WATCH remains in place as some climate models indicate a late and weak La Niña is possible.

During La Niña, northern and eastern Australia typically experience above average spring rainfall, with the first rains of the wet season typically arriving earlier than average in northern Australia. At present, warmer than average seas surrounding Australia—which more typically occur during La Niña—mean some La Niña–like impacts may occur even if thresholds are not exceeded.

 

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 near the equator in the Pacific Ocean have remained close to average for the 5 days ending 11 September, and have remained generally so 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 have eased back slightly in terms of the chance of La Niña, compared to two weeks ago. However, many of the models continue to show borderline cool conditions to be likely and most models include ensemble members which exceed La Niña thresholds. Overall, only one of the surveyed models indicates a clear La Niña is likely to develop and persist across the outlook 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 11 September 2016 is +8.6, edging over the boundary into La Niña range. The 30-day SOI has hovered around +7 for the past week. The 90-day value is currently +5.9.

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 has strengthened compared to two weeks ago as areas of cool anomalies have re-emerged in the western Indian Ocean adjacent to the coastline of Africa. Warm anomalies in the eastern Indian Ocean, between northwestern Australia and Indonesia, have also strengthened compared to two weeks ago. The weekly index value to 11 September was −1.19 °C.

The Indian Ocean Dipole (IOD) index has been below the −0.4 °C negative IOD threshold for sixteen 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 August) 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 was slightly warmer than average. Compared to July these warm anomalies have strengthened, while the pattern of cool anomalies remains similar.

The sub-surface temperature map for the 5 days ending 11 September shows temperatures generally close to average across the sub-surface of the equatorial Pacific. Compared to two weeks ago cool anomalies in the central equatorial Pacific have weakened, again edging closer to average.

Product code: IDCKGEWW00