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.

Over the past fortnight, sea surface temperatures (SSTs) in the eastern equatorial Pacific have cooled significantly. In the western Pacific SSTs have remained similar or warmed slightly. (See: animation of recent SST changes).  The central Pacific has also cooled this past fortnight, but still remains at El Niño levels of warmth.

Warmer than average SSTs continue to surround most of the Australian continent, with large parts of the southern and northern coastline more than 1 °C above average, and waters near Tasmania more than 2 °C above average. To the immediate west of southern WA, SSTs are closer to normal.

Warm anomalies continue to cover much of the Indian Ocean, with large parts of the basin more than 1 °C above average.

The 2015–16 El Niño is in its last stages. Recent changes in the tropical Pacific Ocean and atmosphere, combined with current climate model outlooks, suggest the likelihood of La Niña forming later in 2016 is around 50%, meaning the Bureau's ENSO Outlook is at La Niña WATCH.

Eastern tropical Pacific sea surface temperatures have cooled significantly in the past fortnight, and are now approaching neutral levels. As temperatures under the surface are below average, more surface water cooling is expected. However the atmosphere is only slowly responding to these changes, and hence the Southern Oscillation Index (SOI) and cloudiness near the Date Line continue to fluctuate around El Niño thresholds. 

Six of eight international climate models suggest the tropical Pacific Ocean will return to neutral levels within the next month. By September, seven of eight models suggest La Niña thresholds are likely. However, individual model outlooks show a large spread between neutral and La Niña scenarios.

La Niña is often, but not always, associated with above-average winter-spring rainfall over northern, central and eastern Australia.

Australia's climate is also being influenced by record warm temperatures in the Indian Ocean. The warmth in the Indian Ocean may provide extra moisture for rain systems as they cross Australia during the southern autumn.

During April, equatorial cloudiness near the Date Line has mostly been above average (negative outgoing longwave radiation anomalies). Cloudiness near the Date Line has been consistently above average since March last year.

Cloudiness along the equator near the Date Line typically increases during El Niño (below average outgoing long-wave radiation, or OLR) and decreases during La Niña (above average OLR).

Trade winds for the 5 days ending 24 April remain broadly close to normal across the equatorial Pacific Ocean, except for a small area of westerly wind anomalies on and south of the equator at around 160°W, likely a residual effect from severe tropical cyclone Amos.

The return to near-normal trade winds is consistent with a declining El Niño. Trade winds were consistently weaker than average, and on occasion reversed in direction (i.e. westerly rather than easterly), from the start of 2015 through to January 2016.

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.

Six of eight international climate models suggest the tropical Pacific will return to neutral levels within the next month. By September, seven of eight models suggest La Niña thresholds are likely to be reached. However, individual model outlooks show a large spread between neutral and La Niña scenarios.

The SST (sea surface temperature) anomaly map for March 2016 shows positive SST anomalies extending across the central and eastern equatorial Pacific. Compared to February, positive anomalies have decreased along the equator, but have increased around Australia. This continues the change observed since late 2015, and is typical of El Niño decay.

March values show the NINO3 region in the eastern Pacific cooled by 0.1 °C and the NINO3.4 region cooled by 0.4 °C when compared to February values, continuing the cooling trend initiated in late 2015. Values in the Bureau dataset for NINO3, NINO3.4 and NINO4 were +1.5 °C, +1.5 °C and +1.2 °C respectively.

Positive anomalies persist and have increased over much of the Indian Ocean compared to February. The average temperature of the Southern Indian Ocean for March was a record high temperature for any month on record.

The current 30-day Southern Oscillation Index (SOI) is −20.0 (24 April), falling by over ten points compared with two weeks ago (−7.5 on 10 April).

However, fluctuations of the SOI during Australia's northern wet season (October-April) are not unusual as the passage of tropical systems near Darwin and Tahiti affects atmospheric pressure. During this period, the SOI should be used cautiously; 90-day values can provide more reliable guidance. The current 90-day SOI is −13.2, but has been rising since the start of March, reflecting the easing back of El Niño.

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 Dipole Mode Index value to 24 April was −0.16 °C. The IOD does not typically influence Australian climate during the months December to May, when the monsoon trough is in the southern hemisphere (as positive and negative events are typically unable to form in monsoonal flow).

Currently all international models monitored by the Bureau indicate negative IOD conditions are possible by July. However, model skill is generally lower at this time of year, and outlooks should be used with caution. Negative IOD events are more likely to occur during La Nina.

Sea surface temperatures (SSTs) remain significantly warmer than average across the tropical Indian Ocean.

The four-month sequence of sub-surface temperature anomalies to April shows continued cooling of the sub-surface of the central and eastern Pacific.  A large volume of cooler than usual water is now present beneath almost the entire equatorial Pacific Ocean.

Between March and April, warm anomalies in the top 50m of the equatorial Pacific sub-surface cooled, bringing water temperatures in this region close to average.

The sub-surface temperature map for the 5 days ending 24 April shows that most of the water below the equator in the Pacific Ocean is now largely cooler than average. Only a small area in the top 50 m remains more than 1 °C warmer than average.

The volume of cooler than average water has progressively moved eastwards over the past few weeks. Sub-surface temperature anomalies east of about 170° W are now more than 3 degrees cooler than average in parts. As a result, the equatorial Pacific Ocean surface is likely to cool further, in line with the expected return to ENSO-neutral values within the next month.

 

 

Product code: IDCKGEWW00