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 POAMA forecasts, updated daily
Select to see full-size map of NINIO3.4 SST plumes from POAMA forecasts, updated daily.

Indian Ocean Dipole outlooks

IOD SST plumes from POAMA forecasts, updated daily
Select to see full-size map of IOD SST plumes from POAMA forecasts, updated daily.

Sea surface temperatures (SSTs) remain cooler than average in the central and eastern tropical Pacific for the week ending 14 January. Anomalies are generally similar to those of two weeks ago.

Latest values for the week ending 14 January are: NINO3 −0.9 °C, NINO3.4 −0.7 °C, NINO4 −0.1 °C.

A marine heatwave with large positive SST anomalies persists across the Tasman Sea, extending from southeastern Australia to New Zealand. These shallow warm anomalies developed during the second half of November. Long-lived blocking high pressure systems during both November and December and associated light winds and sunny skies in combination with the background warming trend allowed record temperatures to be reached.

Positive SST anomalies are also present across large areas to the north of Australia, across the Maritime Continent, and in the far western Pacific. This pattern, as well as cooler than average waters in the central and eastern tropical Pacific, are typical during La Niña.

Persistent NINO3 or NINO3.4 values cooler than −0.8 °C are typically indicative of La Niña, while persistent values warmer than +0.8 °C are typical of El Niño.

A weak La Niña pattern continues in the tropical Pacific. This event is likely to be at or near its peak, with most models suggesting this La Niña will end during the southern autumn.

Sea surface temperatures currently show a clear La Niña pattern, with coolest waters concentrated in the eastern Pacific Ocean. Likewise, some atmospheric indicators such as trade winds and cloudiness also show a clear La Niña signal. However, a continuing build-up of warmer water beneath the surface of the western Pacific is a likely precursor to the end of this event.

In order for 2017–18 to be classed as a La Niña year, thresholds need to be exceeded for at least three months. Most climate models surveyed by the Bureau suggest this event is likely to last through the southern summer, and decay in the early southern autumn of 2018, so these thresholds are likely to be met.

La Niña typically brings above average rainfall to eastern Australia during summer, particularly in northern New South Wales and Queensland. However, a weak La Niña will have less influence on Australian rainfall than a strong event. La Niña events can also increase the likelihood of prolonged warm spells for southeast Australia.

The Indian Ocean Dipole (IOD) is currently neutral. IOD events are unable to form between December and April.

Cloudiness near the Date Line remains below average (positive OLR anomalies). Cloudiness in this region has been generally below average since early August 2017.

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 13 January were near average across the central and eastern equatorial Pacific, and slightly stronger than average across the western equatorial Pacific.

During La Niña events, there is a sustained strengthening of the trade winds across much of the tropical Pacific, while during El Niño events there is a sustained weakening, or even reversal, of the trade winds.

International climate models surveyed by the Bureau indicate that it is likely the event has reached, or will soon reach, its peak. Most of the models indicate that equatorial Pacific sea surface temperatures are likely to warm over the coming months, returning to neutral values between late in the austral summer and mid-autumn. However, three of the eight models maintain temperatures near La Niña thresholds well into the austral autumn. Only one out of the eight models maintains La Niña levels into winter (July).

In order for 2017–18 to be considered a La Niña year, NINO3 or NINO3.4 values cooler than −0.8 °C need to be observed for at least three months.

Sea surface temperature (SST) anomalies for December show SSTs were cooler than average in the central and eastern tropical Pacific Ocean and across large areas of the Pacific south of the equator and east of 110°W (i.e. the area to the west of South America). Generally weak warm anomalies were present across most of the remainder of the South Pacific, most of the western Pacific, and parts of the mid-latitudes of the North Pacific. Areas of stronger warm anomalies in excess of two degrees above average were observed between southeastern Australia and New Zealand.

The December value for NINO3 was −0.9 °C, NINO3.4 −0.7 °C, and NINO4 −0.2 °C. All three NINO indices were cooler than November values.

The 30-day Southern Oscillation Index (SOI) to 14 January is −1.6 (90-day value +3.7). The 30-day and 90-day SOI values steadily declined throughout December, and have remained within the neutral range for January to date. This related to the late onset of the monsoon at Darwin, which has so far had only very weak monsoonal flow. Values of the SOI over the past week have risen, but remain on the negative side.

In the austral summer the SOI is more volatile and should be viewed as being a secondary indicator of ENSO.

Sustained positive values of the SOI above +7 typically indicate La Niña while sustained negative values below −7 typically indicate El Niño. Values between +7 and −7 generally indicate neutral conditions.

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 14 January was −0.33 °C. All six of the climate models surveyed by the Bureau indicate that the IOD will remain neutral into the southern hemisphere winter of 2018.

The influence of the IOD on Australian climate is weak during December to April. This is because the monsoon trough shifts south over the tropical Indian Ocean changing wind patterns, which prevents the IOD pattern from being able to form.

The four-month sequence of sub-surface temperature anomalies (to December) shows cool anomalies across most of the central and eastern equatorial Pacific Ocean down to a depth of 200 m. The sub-surface anomalies reached more than 4 °C cooler than average for December. In December, the weak warm anomalies in the far western equatorial Pacific strengthened and shifted eastward compared to November, and were strongest around 160°E and 100 to 150 m below the surface. Both the warm and cool sub-surface temperature anomalies have increased in strength compared to November.

The sub-surface temperature map for the 5 days ending 13 January shows a pool of cooler than average water in the top 100 m of the eastern equatorial Pacific, while in the western equatorial Pacific sub-surface warm anomalies are present between around 100 and 150 m below the surface. Anomalies reached more than two degrees cooler and warmer than average, respectively, in these regions.

The development of a warm pool in the sub-surface of the western equatorial Pacific is a typical precursor to the breakdown of a La Niña. However, the strength of warm anomalies has decreased slightly compared to two weeks ago.

Product code: IDCKGEWW00