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 23 April, sea surface temperatures (SSTs) in the central equatorial Pacific Ocean were close to average. Warm anomalies were present in the far western Pacific, around eastern Australia and in the eastern Pacific. Anomalies greater than +1 °C were located adjacent to South America; these anomalies have cooled over the past few weeks.

Warm SST anomalies also persist across much of the Pacific south of the equator.

The NINO 3.4 region warmed by 0.2 °C in the past fortnight. The NINO3 SST anomaly for the week ending 23 April was +0.7 °C, with NINO3.4 +0.5 °C and NINO4 +0.2 °C.

The El Niño–Southern Oscillation (ENSO) remains neutral. However the Bureau's ENSO Outlook is currently at El Niño WATCH, meaning there is around a 50% chance—twice the normal likelihood—of El Niño developing in 2017.

Tropical Pacific sea surface temperatures (SSTs) have warmed since the start of the year. SSTs in the central tropical Pacific are now 0.5 °C warmer than average, still below the +0.8 °C threshold for El Niño levels. Atmospheric indicators of ENSO remain firmly neutral, although the Southern Oscillation Index (SOI) has returned to negative values over the past fortnight.

International climate models suggest the tropical Pacific Ocean is likely to continue warming in the coming months, though in recent weeks some models have reduced the expected extent of warming. Five of eight models indicate that sea surface temperatures will exceed El Niño thresholds during the second half of 2017; a reduction of two models since the last Wrap-Up release. It should be noted that models have lower accuracy at this time of year.

El Niño is often, but not always, associated with below average winter–spring rainfall over eastern Australia. Of the 27 El Niño events since 1900, 18 resulted in widespread dry conditions for parts of Australia.

The Indian Ocean Dipole (IOD) is currently neutral. Four out of six climate models suggest a positive IOD is likely during winter. When a positive IOD coincides with El Niño, the typical El Niño dry signal expands, and generally stretches further west over eastern and central Australia.

Cloudiness near the Date Line is above average for the first time since winter 2016.

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 23 April were close to average over most of the tropical Pacific.

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.

Climate models surveyed by the Bureau indicate that the central Pacific will continue to warm, with five of eight surveyed models indicating El Niño is likely to form by spring. This is a decrease of two models compared to a fortnight ago, one of which is the Bureau's model POAMA.

It should be noted that model outlooks that span the southern autumn period tend to have lower accuracy than outlooks issued at other times of the year. This means outlooks beyond May should be used with some caution.

SST anomalies for March show sea surface temperatures in the equatorial Pacific Ocean were close to average. Warm anomalies were present in the far eastern Pacific, across much of the Pacific south of the equator, and in the far western Pacific around eastern Australia and much of the Maritime Continent.

The March values for the NINO3, NINO3.4 and NINO4 regions were +0.5 °C, +0.2 °C and 0.0 °C, respectively.

The 30-day Southern Oscillation Index (SOI) to 24 April was −6.6 (90-day value −0.3). SOI values have generally been within the neutral range since mid-October.

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 23 April was +0.2 °C.

The northern Australian wet season is nearing its end. This means the IOD may start to influence the Australian climate. When the monsoon trough and associated wind patterns are located in the southern hemisphere, an IOD circulation is unable to develop. Therefore, the IOD has little influence on Australian climate from December to April.

Current outlooks suggest a neutral IOD for the end of autumn, with some models indicating a positive IOD may form later in winter or spring.

The four-month sequence of sub-surface temperature anomalies (to 20 April) shows the sub-surface of the central to eastern equatorial Pacific Ocean was cooler than average during April. These cool anomalies were similar in strength to those observed for March and February.

Areas of weak warm anomalies were present in the top 150 m of the tropical Pacific west of 160 °E.

The sub-surface temperature map for the 5 days ending 23 April shows temperatures were generally close to average across the sub-surface of the equatorial Pacific Ocean. However, there were small areas of weak warm anomalies in the far western Pacific subsurface at a depth of 100 to 150 m. In the shallow eastern Pacific there were weak warm anomalies, while beneath this there were weak cool anomalies at a depth of 50 to 100 m.

Product code: IDCKGEWW00