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

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 20 January were close to average across the eastern half of the equatorial Pacific Ocean, but remain warmer than average across much of the western equatorial Pacific Ocean. Overall, ocean temperature patterns are consistent with a neutral ENSO state.

Surface temperatures also remain warmer than average around most of Australia, but have cooled slightly compared to two weeks ago. The surface of the ocean is up to 2 degrees warmer than average in some areas of the Great Australian Bight and to the northwest of the Pilbara coast.

Consistent with the neutral state of the Indian Ocean Dipole, there is no longer a large difference in surface temperature between the east and west of the tropical Indian Ocean.

The latest values of the three key NINO indices in the tropical Pacific for the week ending 19 January were: NINO3 0.0 °C, NINO3.4 +0.4 °C and NINO4 +0.8 °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.

Both the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are neutral, and likely to remain so at least until the end of the southern hemisphere autumn. When these main climate drivers are neutral, Australia’s climate can be influenced by more local or short-term climate drivers.

Overall, ENSO indicators are neutral. However, tropical waters near and to the west of the Date Line remain warmer than average, potentially drawing some moisture away from Australia. Additionally, tropical cyclone Tino, in combination with the passage of the Madden-Julian Oscillation, has provided a burst of westerly winds in the western Pacific, with potential to further warm parts of the western Pacific in the coming week or two. Most climate models indicate ENSO will remain neutral until at least the end of the southern hemisphere autumn, meaning it will have limited influence on Australian and global climate in the coming months.

The Indian Ocean Dipole (IOD) is neutral. The IOD typically has little influence on Australian climate from December to April. However, the effects from the strong positive IOD event that occurred in the second half of 2019 persist, with the landscape primed for bushfire weather and heatwaves this summer.

When ENSO and IOD are neutral, other influences can affect Australian climate. The Bureau's Climate Outlooks for the weeks, months and seasons ahead include all the climate influences on Australian weather.

Cloudiness near the Date Line has been above average since mid-December. 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 19 January were weaker than average over the western tropical Pacific, with areas of westerly winds south of the equator. Across the east of the tropical Pacific winds were generally close to average or slightly stronger than average.

This burst of westerly wind is associated with current monsoon-like activity and has been influenced by the Madden-Julian Oscillation. While the effect on winds is expected to pass, this may lead to further warming of sub-surface and then surface waters in the western and 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.

Most international climate models indicate central tropical Pacific sea surface temperatures in the NINO3.4 region will remain at ENSO-neutral levels through the southern hemisphere autumn 2020. One of the eight models reaches the El Niño threshold during March, while another exceeds the La Niña threshold from April until the end of the outlook period (June).

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 much of the western equatorial Pacific Ocean during December, and in a thin band along the equator in the east.

The surface of the ocean was also warmer than average around much of the north, west, and south of Australia during December, and near average to the east.

The December values for NINO3 were +0.4 °C, NINO3.4 +0.4 °C, and NINO4 +0.8 °C. All three NINO indices cooled compared to November. 

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 19 January is −3.3. The 90-day value is −5.1.

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) is currently neutral. The latest weekly value to 19 January was +0.12 °C.

The strong positive IOD event that peaked in October 2019 decayed in late December. This was later than usual for a typical IOD event, due to a later than normal arrival of the monsoon in the southern hemisphere. The 2019 positive IOD was the strongest such event since 1997 and contributed to the widespread warm and dry conditions experienced by Australia during the second half of 2019 and early 2020.

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.

Consistent with the return to neutral, the temperature gradient across the Indian Ocean has reduced significantly over the past two months. Sea surface temperatures are warmer than average across much of the east and west of the basin.

The four-month sequence of equatorial sub-surface temperature anomalies (to December) shows the top 150 m of the western to central equatorial Pacific is warmer than average, with cooler than average waters at a depth of around 50 to 200 m in the east. Small volumes of water reach more than 2 degrees warmer/cooler than average in each region respectively.

The pattern has remained somewhat similar over the past three months, with mostly weak to moderate temperature anomalies. The area of cool anomalies below the surface has migrated eastward over those three months.

For the five days ending 19 January, the sub-surface of the ocean was close to average temperature along the equator. A small volume of slightly warmer than average water is present in the western equatorial Pacific between 100 and 150 m depth, with the warmest area more than two degrees warmer than average.

Product code: IDCKGEWW00