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) for the week ending 1 September remain warmer than average across the western equatorial Pacific Ocean, but overall patterns are consistent with a neutral ENSO state. Most of the northern half of the Pacific Ocean is warmer than average, as well as the southwestern quarter. However, most of the tropical Pacific has cooled over the past fortnight.

Some areas along the eastern half of the equator are cooler than average, with cool anomalies also in the east of the south Pacific close to South America. Also visible are negative anomalies along the southern coastline of the Indonesian archipelago. Cooler waters in this area typically occur during a positive IOD.

SSTs are warmer than average in some areas to the east of Australia and around the southwestern tip of Australia. SSTs are broadly close to average around the rest of Australia.

The latest values of the three key NINO indices in the tropical Pacific for the week ending 1 September are: NINO3 −0.1 °C, NINO3.4 −0.1 °C and NINO4 +0.6 °C. All three NINO indices have cooled compared to two weeks ago.

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 El Niño–Southern Oscillation (ENSO) remains neutral. The positive Indian Ocean Dipole (IOD) continues to be the main influence on Australian climate.

The IOD index has generally been above the positive IOD threshold since mid-July. The broader Indian Ocean patterns of sea surface temperature, cloud, and wind have been positive IOD-like since late May, contributing to dry conditions affecting most of Australia.

All climate models surveyed by the Bureau indicate the positive IOD is likely to continue for the southern hemisphere spring. Typically, a positive IOD brings below average winter–spring rainfall to southern and central Australia, above average daytime temperatures for the southern two-thirds of Australia, and an increased fire risk in the southeast.

The tropical Pacific Ocean remains neutral with respect to the El Niño–Southern Oscillation (ENSO). Atmospheric and oceanic indicators of ENSO are generally close to average, reflecting neutral tropical Pacific cloud and rainfall patterns.

Most climate models indicate the tropical Pacific is likely to remain ENSO-neutral for the rest of 2019 and into early 2020, meaning other climate drivers, like the IOD, are likely to remain as the primary influences on Australian and global weather.

Learn more about the Indian Ocean Dipole.

Cloudiness near the Date Line has fluctuated around average values since late April, 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 1 September were close to average across the central and eastern tropical Pacific, but slightly weaker than average across the far western tropical 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 eight surveyed international climate models indicate central tropical Pacific sea surface temperatures in the NINO3.4 region will remain at ENSO-neutral levels until at least late 2019. One model indicates that values for December and January may pass La Niña thresholds, but the remaining models are all clearly predicting NINO3.4 values within the neutral range.

 

Sea surface temperatures (SSTs) for August were warmer than average across the western tropical Pacific Ocean, near-average for the central tropical Pacific, and cooler than average in some parts of the eastern equatorial Pacific, extending into the south Pacific close to South America.

SSTs were warmer than average to Australia's east, with this warmth extending across the Tasman Sea and well to the east of New Zealand, although anomalies were smaller than during July. SSTs were mostly close to average around the rest of Australia, though there were small areas of both cool and warm anomalies near the southwest of the continent.

The August values for NINO3 were 0.0 °C, NINO3.4 +0.2 °C, and NINO4 +0.7 °C. All three NINO indices cooled compared to July.

The 30-day Southern Oscillation Index (SOI) is neutral, with the value for the 30 days ending 1 September at −3.8. The 90-day value was −6.1.

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) remains positive, with the latest weekly index value to 1 September at +0.98 °C.

The overall pattern of sea surface temperatures has remained generally consistent with a positive IOD pattern since late May, with warmer than average sea surface temperatures in the central and western tropical Indian Ocean, and average to cooler than average waters in the eastern tropical Indian Ocean, to the northwest of Australia and south of Indonesia.

Typically, to be considered a positive IOD event, index values need to remain above the positive threshold (+0.4 °C) for at least eight weeks. The index value has been above the threshold in six of the last seven weeks, and was also above the threshold from late May to mid-June.

All six international climate models surveyed by the Bureau indicate the IOD will remain positive through November, and will decline significantly in strength by December when values for two models drop below the threshold. IOD events typically dissipate by early summer as the monsoon trough moves into the southern hemisphere, which changes the broadscale wind patterns over the IOD region, and means the IOD pattern is unable to be sustained.

A positive IOD often results in below average winter–spring rainfall over southern and central Australia. It also typically means warmer than average winter-spring days for the southern two-thirds of Australia.

The four-month sequence of equatorial sub-surface temperature anomalies (to August) shows a pattern of weak cool anomalies extending across the equatorial Pacific, at a depth of around 100 to 200 m in the west of the Basin, rising to 0 to 100 m depth in the east. Weak warm anomalies extend across most of the column depth in the central to western equatorial Pacific above and below this band of cool anomalies. This general pattern has been in place since May.

Anomalies, both warm and cool, are mostly within 2 degrees of average, though some areas of cool anomalies more than 2 degrees cooler than average exist in the east of the Pacific sub-surface.

For the five days ending 1 September water temperatures were close to average across most of the sub-surface of the equatorial Pacific. This pattern is consistent with ENSO-neutral conditions.

Product code: IDCKGEWW00