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 13 October remain warmer than average across the western to central equatorial Pacific Ocean, and slightly cooler than average in parts of the east, 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 areas south of 30°S.

Cool anomalies remain in areas of the tropical Pacific east of 120°W, in parts of the South Pacific close to South America, and across waters between Australia and Papua New Guinea, the Arafura Sea, and on the southern side of the Indonesian archipelago. SSTs are more than 2 degrees cooler than average in some areas close to Sumatra. Cooler waters in the eastern Indian Ocean typically occur during a positive IOD. Warm anomalies have strengthened off the Horn of Africa, now reaching more than 2 degrees warmer than average. These strong warm anomalies off Africa, combined with very strong cool anomalies off the island of Sumatra reflect the current very strong positive values of the IOD index. (See weekly Indian Ocean SST anomaly map.)

The latest values of the three key NINO indices in the tropical Pacific for the week ending 13 October are: NINO3 +0.1 °C, NINO3.4 +0.5 °C and NINO4 +0.9 °C. All three NINO indices have warmed 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.

A strong positive Indian Ocean Dipole (IOD) continues to influence Australian and global climate. The El Niño–Southern Oscillation (ENSO) remains neutral.

The current positive Indian Ocean Dipole event has strengthened significantly over the past month. The latest weekly value of +2.15 °C is the strongest positive weekly value since at least 2001 (when the Bureau's weekly dataset commenced), and possibly since 1997, when strong monthly values were recorded. Over the past month, strong easterly trade winds across the tropical Indian Ocean aided upwelling of cooler water in the eastern Indian Ocean. At the same time, very warm waters off the Horn of Africa have caused an even greater temperature gradient across the basin.

Given the strength of the trade winds, the IOD may strengthen further over the next fortnight. However, international climate models surveyed by the Bureau indicate the positive IOD is unlikely to persist far into summer. IOD breakdown occurs when the monsoon trough moves into the southern hemisphere in early December. With the monsoon trough having a record-late retreat from India this year, the shift into the southern hemisphere may also be later than usual.

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. Most indicators of ENSO are near-average, although the Southern Oscillation Index (SOI) is negative (El Niño-like) due to very high atmospheric pressure at Darwin. The corresponding pressure in Tahiti is largely within normal bounds. This suggests the negative SOI is not related to a developing El Niño, but rather is likely related to the strong positive Indian Ocean Dipole and the cooler waters between Australia and Indonesia.

Climate models forecast neutral ENSO for the remainder of 2019 and into the first quarter of 2020. When ENSO is neutral, it has little effect 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. However, cloudiness near the Date Line has generally remained below average since early to mid-September.

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 October were close to average across most of the tropical Pacific, but weaker than average in the far west to the north of the equator.

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.

In the Indian Ocean, trade winds have been much stronger than average, typical of a positive IOD phase.

All eight surveyed international climate models indicate central tropical Pacific sea surface temperatures in the NINO3.4 region will remain at ENSO-neutral levels into early 2020.

One model indicates that values may move towards La Niña thresholds over summer, but does not reach the threshold until March. The remaining seven models are all maintain NINO3.4 values within the neutral range throughout the outlook period.

Sea surface temperatures (SSTs) for September 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 in areas around eastern Australia and far southwestern Australia. SSTs were mostly close to average around the rest of Australia, though there were small areas of cool anomalies in some areas to the north of Australia.

The September values for NINO3 were −0.1 °C, NINO3.4 0.0 °C, and NINO4 +0.7 °C. NINO3 and NINO3.4 cooled compared to August, while NINO4 held steady.

The 30-day Southern Oscillation Index (SOI) for the 30 days ending 13 October was −8.5. The 90-day value was −7.2. Recent negative SOI values are 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 strongly positive, with the latest weekly index value to 13 October at +2.15 °C. This is the highest weekly value observed in the Bureau's dataset which extends from 2001 to present, and possibly the highest since 1997. Values for each of the last four weeks have been above the old record set before the current event. The previous record was +1.48 °C for the week ending 5 November 2006.

The very strong positive values of the IOD are due to the strong temperature gradient across the Indian Ocean (see weekly SST map for the Indian Ocean). SSTs to the south of the Indonesian islands of Sumatra and Java reach more than 2 degrees cooler than average for the week ending 13 October, while warm anomalies close to the Horn of Africa reach more than 2 degrees warmer than average.

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.

All six international climate models surveyed by the Bureau indicate the IOD will remain positive into December.

The retreat of the Southwest Indian Monsoon has been very slow this year, and models are indicating a slower break down of the IOD than usual. However, it remains unlikely that the positive IOD will persist far into summer. IOD events dissipate 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.

For more info on the southwest monsoon withdrawal, see the Indian Meteorological Department.

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 September) shows cool anomalies extending across much of the equatorial Pacific, at a depth of around 100 to 200 m in the west of the Basin, and 0 to 150 m depth in the east. Weak warm anomalies extend across most of the column depth between about 160°E and 160°W. This general pattern has been in place since July.

Cool anomalies in the east have intensified in September compared to August and reach up to 3 degrees cooler than average in a small region, while warm anomalies in the west are weaker, reaching up to 2 degrees warmer than average.

For the five days ending 13 October water temperatures were close to average across much of the sub-surface of the equatorial Pacific. However, there was a volume of warmer than average water in the east between 150°W and 100°W at around 100 m depth, with anomalies reaching more than 4 degrees cooler than average in a small region. A smaller volume of weaker warm anomalies was also present in the west centred around 100 to 150 m depth near the Date Line, with anomalies reaching more than 2 degrees warmer than average.

Over the past two weeks warm anomalies in the eastern equatorial Pacific have replaced what was previously cool anomalies.

Product code: IDCKGEWW00