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.

For the week ending 10 September, sea surface temperatures (SSTs) were close to average across most of the equatorial Pacific Ocean. Cool anomalies have continued to develop near the equator in the eastern Pacific, while warm anomalies remain in the far western Pacific. There are generally weak warm anomalies present across much of the South Pacific, with stronger anomalies around the east coast of Australia.

The NINO3.4 SST anomaly has continued to cool during the past fortnight and is now −0.3 °C. NINO3 has also cooled to −0.4 °C, while NINO4 has cooled to +0.2 °C.

Sea surface temperatures (SSTs) have steadily cooled over the central and eastern tropical Pacific for the past two months, but remain well within the neutral ENSO range. Temperatures at and below the surface are now slightly cooler than average. Other indicators of ENSO, such as the Southern Oscillation Index (SOI), cloudiness near the Date Line and trade winds also remain at neutral levels.

Most international climate models surveyed suggest the tropical Pacific Ocean may cool further, but persist at ENSO-neutral levels for the rest of 2017. Two of the eight models approach La Niña thresholds around the end of the year, which is typically when ENSO events reach their peak.

The Indian Ocean Dipole (IOD) is neutral, though index values have generally been weakly positive for the past five months. Most climate models suggest the IOD is likely to remain neutral. However, two of the six climate models surveyed suggest a positive IOD may develop during spring. If a positive IOD eventuated it would likely be short-lived as IOD events typically break down by December as the monsoon trough moves south towards Australia.

Positive IOD events are typically associated with below average spring rainfall, and increased spring–summer fire potential over central and southern Australia, while La Niña-like patterns tend to promote above-average spring rainfall in the south and east. Hence Australia faces some competing, though weak, climate drivers in the months ahead.

Cloudiness near the Date Line during the past two weeks has fluctuated around average values, as it has done since mid-April.

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

Trade winds for the 5 days ending 10 September were slightly stronger than average over the western tropical Pacific and near average in the central and eastern tropical Pacific. These stronger trades may be assisting the cooling of sea surface temperatures.

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.

International climate models surveyed by the Bureau indicate that ENSO-neutral conditions are likely to persist at least until late 2017. Most models indicate further cooling of the tropical Pacific sea surface temperatures during spring and summer may be likely. However, six out of eight models stay neutral for the remainder of the year, with only two models reaching La Niña thresholds near the end of 2017. Historically this is close to the time when ENSO events peak.  

Sea surface temperature (SST) anomalies for August show SSTs were close to average along the equator in the Pacific Ocean. Warm anomalies were located across most of the south Pacific with the strongest anomalies occurring off the east Australian coastline and to the east of New Zealand. Large parts of the North Pacific between Indonesia and Japan also had SSTs of more than 1 °C warmer than average.

The August values for the NINO3.4, NINO3 and NINO4 regions were 0.0 °C, 0.0 °C and +0.4 °C, respectively. All three August values cooled with respect to July, but remain firmly within the neutral range.

The 30-day Southern Oscillation Index (SOI) to 10 September is +6.8 (90-day value +3.3), within the ENSO neutral range.

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 Indian Ocean Dipole (IOD) is neutral. The weekly index value to 10 September was +0.3 °C, and has persisted at levels just shy of the positive IOD threshold (+0.4 °C) for the past four to six weeks.

Most of the climate models surveyed by the Bureau indicate that the IOD will remain neutral during spring. Two models suggest a positive IOD remains a possibility during spring. A positive IOD is typically associated with below average spring rainfall over southern and central Australia.

IOD events typically decay during spring, and the influence of the IOD on Australian climate is weak during the months December to May. This is because the monsoon trough shifts south over the tropical Indian Ocean changing wind patterns, which prevents the IOD pattern from being able to form.

The four-month sequence of sub-surface temperature anomalies (to August) shows cool anomalies developing in the central to eastern equatorial Pacific Ocean down to a depth of 150 m. In some areas these anomalies are up to 3.0°C cooler than average for the month of August. Weak warm anomalies persist in the shallow sub-surface waters of the western equatorial Pacific Ocean.

The sub-surface temperature map for the 5 days ending 11 September shows cooler than normal water temperatures from 50 to 150 m depth in the central to eastern equatorial Pacific Ocean. Sub-surface water temperatures are generally close to average elsewhere across the equatorial Pacific Ocean.

Product code: IDCKGEWW00