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 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) are slightly warmer than average across the entire tropical Pacific Ocean, but remain at levels consistent with neutral ENSO. This anomalous warmth sits just to the north of the equator, which is somewhat unusual; typically ENSO-related warming is centred on the equator. South of the equator, surface temperatures are mostly near-average, except in the far western tropical Pacific which is also warmer than average.

The latest values of the key NINO indices in the tropical Pacific for the week ending 9 September are: NINO3 +0.2 °C, NINO3.4 +0.3 °C and NINO4 +0.6 °C, reflecting the concentration of anomolous warmth in the western Pacific.

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.

Around Australia, parts of the Coral Sea and Tasman Sea are warmer than usual; but for most of the waters around Australia SSTs are close to average for this time of year.

The El Niño–Southern Oscillation (ENSO) remains neutral. However model outlooks continue to indicate El Niño is possible from late spring 2018. When assessed with current observations, the Bureau's ENSO Outlook stands at El Niño WATCH, meaning there is approximately a 50% chance of El Niño forming in the coming months—double the normal chance.

There were only small changes to most indicators of ENSO in the past fortnight. The central and eastern tropical Pacific Ocean are warmer than average, with greatest warmth in the central to western Pacific (NINO4; +0.6 °C), while water below the surface remains somewhat warmer than average. Atmospheric indicators generally remain neutral, although trade winds are slightly weaker over parts of the western Pacific. A weakening of the trade winds is one of the most important precursors at this point for any possible El Niño, and will be watched closely.

Most international climate models surveyed by the Bureau indicate that the tropical Pacific is likely to warm to El Niño thresholds by the end of spring. El Niño during spring typically results in below-average rainfall in eastern and northern Australia. In summer, this drying influence retracts to tropical regions of Australia, although the possibility of high temperatures elsewhere remains high.

The Indian Ocean Dipole (IOD) is neutral. However, two of six international climate models suggest a positive IOD event may develop before the end of spring. A positive IOD during spring typically reduces rainfall in central and southern Australia, and can exacerbate any El Niño-driven rainfall deficiencies.

Regardless of El Niño or positive IOD developing, the climate outlook for spring is for a continuation of drier and warmer than average conditions across eastern and southwest Australia.

Cloudiness near the Date Line has fluctuated around average values since mid-August.

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 five days ending 9 September were near average across the equatorial Pacific, with slightly weaker than average trades to the north of the equator in the far western to central Pacific.

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.

All of the surveyed international climate models predict further warming of central equatorial Pacific sea surface temperatures (SSTs) over the coming months.

Seven of the eight surveyed models suggest SSTs are likely to reach or exceed El Niño thresholds by the end of spring, with the majority suggesting values will remain at or above the threshold into early 2019.

Sea surface temperature (SST) for August were slightly warmer than average across the equatorial Pacific Ocean, but within the neutral ENSO range. The South Pacific, parts of the Maritime Continent, and large parts of the North Pacific were warmer than average.

The August values for NINO3 were +0.2 °C, NINO3.4 +0.3 °C, and NINO4 +0.6 °C.

The 30-day Southern Oscillation Index (SOI) to 9 September was −6.2, and the 90-day SOI was −4.6. The 30-day SOI value has fluctuated around El Niño threshold values for around three weeks, but is yet to show a consistent and stable pattern.

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 weekly index value to 9 September was +0.28 °C.

Two of the six international climate models surveyed by the Bureau suggest that a positive IOD may develop.

The four-month sequence of sub-surface temperature anomalies (to August) shows a persistent pool of warmer than average water in the equatorial Pacific. However, during August a pool of slightly cooler than average water also emerged in the shallow sub-surface of the eastern equatorial Pacific. Compared to earlier months, the pool of warmer than average water has cooled slightly, but weak warm anomalies remain evident in the central equatorial Pacific sub-surface for August.

Temperatures for the five days ending 9 September show water was warmer than average below the surface of a large area of the central equatorial Pacific, between 100 m and 200 m depth.

Compared to weeks ago, the subsurface warm anomalies have increased and extended further eastward. These current anomalies are similar to those present during July. While the overall state of the sub-surface remains consistent with neutral ENSO, the shift eastwards of anomalously warm water has sometimes in the past been a precursor to El Niño.

Product code: IDCKGEWW00