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 18 August 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. Across the southeastern quarter, SSTs are close to average, with some areas along the equator and close to South America in the tropics are slightly cooler than average.

SSTs are also warmer than average in waters to the east of Australia and around the southwestern tip of Australia. SSTs are broadly close to average around the rest of Australia, with weak negative anomalies along much of the coast of South Australia and a small area of around the Gascoyne coast in Western Australia. Also visible are negative anomalies along the southern coastline of the Indonesian archipelago. Cooler waters in this area typically occur during a positive IOD.

The latest values of the three key NINO indices in the tropical Pacific for the week ending 18 August are: NINO3 −0.1 °C, NINO3.4 +0.2 °C and NINO4 +0.8 °C. While NINO3 held steady over the past fortnight, NINO4 and NINO3.4 have cooled slightly.

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 Indian Ocean is expected to be the dominant driver of Australia's climate over the coming months.

The Indian Ocean Dipole (IOD) index has been above the positive IOD threshold for four of the past five weeks, with values strengthening in the past month. However, the broader Indian Ocean patterns of sea surface temperature, cloud, and wind have been positive IOD-like since late May.

All climate models surveyed by the Bureau forecast positive IOD conditions 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 increased fire risk in the southeast.

The El Niño–Southern Oscillation (ENSO) remains neutral—neither El Niño nor La Niña. Atmospheric and oceanic indicators of ENSO are mostly close to average, reflecting neutral tropical Pacific cloud patterns and rainfall.

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

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 18 August were close to average across the central and eastern tropical Pacific, but weaker than average across the 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 within the neutral range.

 

SSTs for July were warmer than average across the western tropical Pacific Ocean, with the eastern half cooling to near-average levels compared to June.

SSTs were warmer than average to Australia's east, extending across the Tasman Sea and well to the east of New Zealand, with temperatures up to two degrees warmer than average for much of this region. The rest of the Australian region recorded near-average SSTs during July, with just some weak negative anomalies in the western half of the Great Australian Bight.

The July values for NINO3 were +0.3 °C, NINO3.4 +0.5 °C, and NINO4 +0.8 °C, with the NINO3 and NINO3.4 cooling compared to June and NINO4 warming slightly.

The 30-day Southern Oscillation Index (SOI) is close to zero. The SOI for the 30 days ending 18 August was +0.7, with the 90-day value −6.8.

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 latest weekly value of the Indian Ocean Dipole (IOD) index to 18 August is +0.79 °C. The IOD index has exceeded the positive IOD threshold in four of the past five weeks.

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.

All six international climate models surveyed by the Bureau indicate positive IOD values will persist through the southern hemisphere spring.

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 July) shows a pattern of weak shallow warm anomalies in the central to western equatorial Pacific, with weak cool anomalies extending across much of the equatorial Pacific at greater depth. This pattern has been generally similar since May. Anomalies, both warm and cool, are mostly within 1.5 degrees of average.

Temperatures for the five days ending 18 August show waters were close to average across most of the sub-surface of the equatorial Pacific. A small volume of cooler than average water was present around 50 to 100 m depth near 120°W in the eastern equatorial Pacific, with anomalies reaching more than 4 degrees cooler than average. Elsewhere, sub-surface waters were all within 2 degrees of average.

This pattern is consistent with ENSO-neutral conditions.

Product code: IDCKGEWW00