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.

The SST map for January shows below average SSTs extending along the equator in the western and central tropical Pacific Ocean, extending into the tropics south of the equator in the east of the basin. The strength of these anomalies has decreased in eastern parts of the basin compared to December but has increased in the western half of the basin.

SSTs were warmer than average in much of the area around Australia, particularly in the northwest and southeast.

January values of the three key NINO indices were: NINO3 −0.4 °C, NINO3.4 −0.8 °C, and NINO4 −0.9 °C.

The sea surface temperature (SST) map for the tropical Pacific Ocean for the week ending 14 February shows cool anomalies extending along the equator through the central and western Pacific, parts of the equator in the eastern Pacific, and extending to the south of the equator in the eastern Pacific. Warm anomalies remain around the Maritime Continent and in the waters close to parts of Australia.

The latest values of the three NINO indices in the tropical Pacific for the week ending 14 February were: NINO3 −0.5 °C, NINO3.4 −0.7 °C, NINO4 −0.9 °C. NINO3 and NINO4 have strengthened slightly 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 30-day Southern Oscillation Index (SOI) for the 30 days ending 14 February was +13.3. The 90-day SOI value was +15.3. Recent 30-day values have continued their gradual decline from a peak of around +20 maintained for much of early to mid-January.

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.

Trade winds for the 5 days ending 14 February were stronger than average over much of the western half of the tropical Pacific, and near average strength in the centre and east. Trade wind strength has increased compared to two weeks ago.

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.

The Madden–Julian Oscillation (MJO) is currently strong and located over the central Pacific Ocean.

The MJO is expected to move out of the central Pacific and cross the Americas during late February and early March. When the MJO is over the Americas at this time of the year, tropical areas across northern Australia would typically be drier than average.

Sea surface temperatures (SSTs) in the Indian Ocean are warmer than average across much of the mid-latitudes in the southern half of the basin. Warm SST anomalies to the northwest of Western Australia may be influencing local weather patterns.

The Indian Ocean Dipole (IOD) is neutral. The latest weekly value of the IOD index to 14 February was −0.18 °C.

All of the five surveyed climate models expect the IOD to remain neutral through early autumn. IOD events are typically unable to form between December and April. This is because the monsoon trough shifts south over the tropical Indian Ocean and alters wind patterns, preventing the IOD pattern from being able to form.

Cloudiness near the Date Line has generally been below average since early to mid-March 2020. While still below average, the tendency for reduced cloudiness was lower during February than in the previous three months.

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

The four-month sequence of equatorial Pacific sub-surface temperature anomalies (to 31 January) shows cooler than average water extending across the top 200 m of the sub-surface of the equatorial Pacific east of around 160°E. The strength and spatial extent of cooler than average water has remained fairly consistent since September, with some strengthening in January.

Warm anomalies persist across large parts of the column depth west of the Date Line, with warm anomalies underlying the shallower cool anomalies between the Date Line and 160°E. These warm anomalies have strengthened month-on-month since October.

For the five days ending 14 February, sub-surface temperatures were above average between around 100 and 250 m depth west of the Date Line, reaching more than three degrees above average around 150°E and 150 m depth. In the eastern half of the equatorial Pacific, cool anomalies persist across the top 150 m, reaching four degrees cooler than average in a small region around 140°W and 100 m depth. Anomalies in both the west and east have strengthened compared to two weeks ago.

The 2020–21 La Niña continues to influence Australia and the broader Pacific Basin. In terms of typical indicators of La Niña, however, this event has peaked. Climate model outlooks indicate the El Niño–Southern Oscillation (ENSO) will return to neutral during autumn, that is, neither La Niña nor El Niño. The wetter influence from La Niña is likely to continue for the shorter term, with three-month climate outlooks indicating above average rainfall is likely for parts of northern Australia.

In the tropical Pacific Ocean, sea surface temperatures remain similar to last fortnight's, with a cooler than average tongue of water still present across the central to western Pacific. Beneath the surface, cooler water is still present. In the atmosphere, the Southern Oscillation Index (SOI) still clearly remains within the La Niña range, and cloudiness near the Date Line is below average, a typical La Niña atmospheric pattern.

The Madden–Julian Oscillation (MJO) is currently located over the central Pacific Ocean and is expected to move eastwards during the coming fortnight towards the tropical Americas. When the MJO is over the Americas at this time of the year, tropical areas across northern Australia would typically be drier than average.

The Southern Annular Mode (SAM) has recently been positive, but forecasts expect a return to neutral values in coming days. Typically, a positive SAM during summer increases the chance of above average rainfall across parts of eastern Australia. During the autumn months, SAM has little influence on Australian rainfall.

The Indian Ocean Dipole (IOD) is currently neutral. The IOD typically has little influence on Australian climate from December to April.

Climate change is also influencing the Australian climate. Australia's climate has warmed by 1.44 ± 0.24 °C over the period 1910–2019, while recent decades have seen increased rainfall across northern Australia during the northern wet season (October–April), with more high-intensity, short-duration rainfall events.

The Southern Annual Mode (SAM) has recently been positive but is expected to remain neutral into at least early March.

During summer positive SAM increases the chance of above average rainfall across parts of eastern Australia. Heading into autumn, the influence of SAM on rainfall decreases.

The 2020–21 La Niña has passed its peak, with most of the international climate models surveyed by the Bureau anticipating NINO3.4 will return to borderline or neutral values by mid-autumn. It is typical for La Niña to continue to influence Australian climate, even as the La Niña weakens.

La Niña increases the likelihood of above-average rainfall across much of northern and eastern Australia during summer and early autumn. Below-average daytime temperatures are typically observed for large parts of the country, particularly Queensland. It also increases the chance of tropical cyclones and earlier first rains of the northern wet season, as we saw this season.

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