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

While the SOI is an important index that tracks changes in tropical air pressure, we consider a much wider range of atmospheric and oceanic conditions when we assess the status of ENSO. This includes winds, clouds, ocean currents and both surface and sub-surface ocean temperatures, as well as outlooks for the months ahead.

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 Bureau model forecasts, updated daily
Select to see full-size map of NINIO3.4 SST plumes from Bureau model forecasts, updated daily.

Indian Ocean Dipole outlooks

IOD SST plumes from Bureau model forecasts, updated daily
Select to see full-size map of IOD SST plumes from Bureau model forecasts, updated daily.

Sea surface temperatures (SSTs) for the week ending 29 March were slightly warmer than average across most of the equatorial Pacific Ocean, but remain within the neutral range. Water has cooled slightly in the western equatorial Pacific compared to two weeks ago.

SSTs also remain warmer than average around most of Australia. SSTs are up to two degrees warmer than average around most of Western Australia, and up to one degree warmer than average across large parts of the Coral Sea and the Tasman Sea.

The latest values of the three key NINO indices in the tropical Pacific for the week ending 29 March were: NINO3 +0.4 °C, NINO3.4 +0.5 °C and NINO4 +0.6 °C. 

Persistent NINO3 or NINO3.4 values warmer than +0.8 °C are typical of El Niño, while persistent values cooler than −0.8 °C typically indicate La Niña.

The tropical Pacific remains neutral with respect to the El Niño–Southern Oscillation (ENSO). Atmospheric and oceanic indicators of ENSO including the Southern Oscillation Index (SOI), trade winds, cloudiness near the Date Line, and sea surface and sub-surface temperatures in the tropical Pacific Ocean all continue to persist at levels consistent with neutral ENSO.

Six of the eight climate models surveyed by the Bureau indicate that ENSO is likely to stay neutral through the southern hemisphere winter, meaning it may have limited influence on Australian and global climate in the coming months. The remaining two models suggest La Niña may develop during winter. However, ENSO predictions made during autumn tend to have lower accuracy than predictions made at other times of the year. This means that current ENSO forecasts beyond May should be used with some caution.

The Indian Ocean Dipole (IOD) is neutral. The IOD typically has little influence on Australian climate from December to April. Of the six international climate models surveyed, most indicate neutral IOD for the coming months. One model briefly reaches positive levels at the end of autumn, while several tend towards negative levels during the southern hemisphere winter. However, similar to ENSO, accuracy of IOD forecasts beyond autumn is low.

Recently the Southern Annular Mode (SAM) has been positive but is forecast to return to neutral levels over the next few days and then remain neutral for the following three weeks. SAM has little influence upon Australian rainfall in autumn.

The Madden–Julian Oscillation (MJO) is forecast to move into the Australian region, but its influence on rainfall over northern Australia is likely to be short-lived or insignificant, as it weakens rapidly in early April.

Cloudiness near the Date Line has generally been above average since mid-December, although there was a period of below average cloudiness earlier during March. Overall cloud patterns are consistent with neutral ENSO.

Equatorial cloudiness near the Date Line typically increases during El Niño (negative OLR anomalies) and decreases during La Niña (positive OLR anomalies).

Trade winds for the 5 days ending 29 March were close to average across most of  the tropical Pacific, and slightly stronger than average in part of the far western tropical Pacific. Overall, the trade wind pattern is consistent with neutral ENSO conditions.

During El Niño there is a sustained weakening, or even reversal, of the trade winds across much of the tropical Pacific. Conversely, during La Niña, there is a sustained strengthening of the trade winds.

Six of the eight international climate models surveyed by the Bureau indicate central tropical Pacific sea surface temperatures in the NINO3.4 region will remain at ENSO-neutral levels through the southern hemisphere winter. The remaining two models exceed the La Niña threshold during winter.

ENSO predictions made during autumn tend to have lower accuracy than predictions made at other times of the year. This means that current ENSO forecasts beyond May should be used with some caution.

ENSO events, that is, either El Niño or La Niña, typically begin to develop during autumn, before strengthening in winter/spring. The Bureau will continue to closely monitor the potential for either to develop this year.

The surface of the ocean remained warmer than average across the western equatorial Pacific Ocean during February, while the eastern half was generally close to average.

The surface of the ocean was also warmer than average around much of Australia during February.

The February values of the three key NINO indices were: NINO3 +0.1 °C, NINO3.4 +0.3 °C, and NINO4 +0.8 °C.

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 29 March was −5.8, falling around 5 points over the past fortnight. The 90-day value was −2.0. Both values are well within the ENSO neutral range.

Sustained negative values of the SOI below −7 typically indicate El Niño while sustained positive values above +7 typically indicate La Niña. Values between +7 and −7 generally indicate neutral conditions. 

The Indian Ocean Dipole (IOD) is currently neutral. The latest weekly value to 29 March is +0.1 °C.

The IOD typically has little influence on Australian climate from December to April. When the monsoon trough shifts southwards into the southern hemisphere, it changes the broadscale wind patterns, meaning that the IOD pattern is unable to form.

Of the six international climate models surveyed, most indicate a neutral IOD for the coming months. One model briefly reaches positive levels at the end of autumn, while several tend towards negative levels during winter. However, at this time of year the accuracy of IOD forecasts beyond autumn is low.

The four-month sequence of equatorial sub-surface temperature anomalies (to 28 March) shows the top 150 m of the western half of the equatorial Pacific is warmer than average, reaching up to two degrees warmer than average. Slightly cooler than average waters are present below these warm anomalies, and also extend in a narrow band across the eastern half of the equratorial Pacific, rising to a depth of around 50 m at the eastern edge of the equatorial Pacific.

The pattern has remained somewhat similar since December, with mostly weak to moderate temperature anomalies.

For the five days ending 29 March, temperatures were slightly warmer than average in a small region of the eastern Pacific between 50 and 100 m depth. This warmth has shifted eastward over the past month, and while the warmest temperature anomalies remain similar to two weeks ago, only a small volume reaches more than two degrees warmer than average.

In the central equatorial Pacific a small volume of cooler than average water has developed over the past fortnight, reaching more than two degrees cooler than average in a region just east of the Date Line between 100 and 200 m depth.

Elsewhere in the sub-surface of the equatorial Pacific Ocean, sub-surface temperatures were generally close to average.

Product code: IDCKGEWW00