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

Following links open in new window

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 15 September remain warmer than average west of the Date Line in the 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.

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. Surface waters between Australia and Papua New Guinea, across the Arafura Sea, and on the southern side of the Indonesian archipelago are also cooler than average. 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 southwest Australia.

The latest values of the three key NINO indices in the tropical Pacific for the week ending 15 September are: NINO3 −0.3 °C, NINO3.4 −0.2 °C and NINO4 +0.5 °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 while the positive Indian Ocean Dipole (IOD) continues to influence the climate of Australia and other parts of the globe.  

A moderate to strong positive Indian Ocean Dipole continues, characterised by cooler waters to the northwest of Australia and warmer waters further west. While the IOD index has been above threshold for most of the past two months, the general sea surface temperature and cloud patterns have shown positive IOD characteristics since the end of May. It's likely much of the low rainfall over southern and central Australia during winter has been a result of the positive IOD.

All international climate models surveyed by the Bureau indicate the positive IOD is likely to persist for the southern hemisphere spring. At the beginning of summer, an IOD pattern normally breaks down as the monsoon trough migrates into the southern hemisphere.

Typically, a positive IOD brings below average winter-spring rainfall to southern and central Australia, with warmer days for the southern two-thirds of the country. Positive IOD events are often associated with a more severe fire season for southeast Australia. Learn more about the Indian Ocean Dipole.

In the tropical Pacific Ocean, the El Niño–Southern Oscillation (ENSO) remains neutral. Parts of the eastern tropical Pacific are now slightly cooler than average but remain in the neutral range. Most atmospheric indicators are neutral, although the Southern Oscillation Index (SOI) has fallen over the past fortnight due to very high atmospheric pressures at Darwin.

International climate models predict a neutral ENSO state is the most likely scenario for the remainder of 2019, and into early 2020. When ENSO is neutral, it has little influence on Australian and global climate, meaning other influences are more likely to dominate. 

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 15 September were close to average across the central and eastern tropical Pacific, but 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 may approach El Niño thresholds for December through February, while one other model reaches the La Niña threshold in February. The remaining six 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) for the 30 days ending 15 September was −11.9. The 90-day value was −9.0. Values have become more negative over the past fortnight. This recent strengthening of negative SOI values is due to very high atmospheric pressure over Darwin.

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 15 September at +1.02 °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 north 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 eight of the last nine 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 into December. IOD events usually dissipate by early summer as the monsoon trough moves into the southern hemisphere, which changes the broadscale wind patterns over the IOD region and returns sea surface temperatures to near average. Models are indicating a slower break down of the IOD than usual, but it remains unlikely that the positive IOD influence will persist far into summer.

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 15 September water temperatures were close to average across much of the sub-surface of the equatorial Pacific. However, there was a volume of cooler than average water in the east centred around 100 m depth and 120°W, with anomalies reaching more than 4 degrees cooler than average in a small region, and a volume of weaker warm anomalies in the west centred around 100 to 150 m depth near the Date Line, with anomalies reaching more than 2 degrees warmer than average.

Product code: IDCKGEWW00