ENSO Wrap-Up
Current state of the Pacific and Indian Ocean

Little change in the tropical Pacific Ocean

Issued on Tuesday 26 August 2014 |

Despite tropical Pacific Ocean temperatures remaining at neutral levels, models suggest El Niño development remains possible during the coming months.

The brief weakening of the trade winds over the Pacific Ocean earlier in August produced little warming of tropical sea surface temperatures. However, waters below the surface of the Pacific have warmed during the past few weeks, and therefore above-average temperatures near the surface are likely to persist or strengthen over the coming months.

Four of the seven climate models surveyed by the Bureau suggest El Niño is likely by the Australian summer of 2014–15. These model outlooks and current observations mean the Bureau’s ENSO Tracker remains at WATCH status. This indicates the chance of El Niño developing in the coming months is at least 50%, which is around double the normal likelihood of an event.

El Niño-like weather patterns can occur even if an event hasn’t become fully established. In 2014, these have included below-average rainfall across parts of eastern Australia, above-average daytime temperatures and a number of significant frost events.

The Indian Ocean Dipole (IOD) remains negative. Model outlooks suggest this negative IOD event is unlikely to persist for long, with models suggesting the IOD will return to neutral in early spring. A negative IOD pattern typically brings wetter winter and spring conditions to inland and southern Australia.

Next update expected on 9 September 2014 | print version

Weekly sea surface temperatures

During the past two weeks, sea surface temperatures (SSTs) have cooled in the eastern tropical Pacific and warmed in the far western tropical Pacific. Positive anomalies are present along most of the equatorial Pacific, with anomalies close to average in an area around 150°W in the central Pacific (see SST anomaly map for the week ending 24 August). Warm anomalies also remain in areas of the eastern Indian Ocean and across most of the northern Pacific Basin.

Click to see full-size map showing temperatures in the tropical Pacific.
Baseline period 1961–1990.
Index Previous Current Temperature change
(2 weeks)
NINO3 +0.5 +0.5 no change
NINO3.4 +0.2 +0.3 0.1 °C warmer
NINO4 +0.7 +0.6 0.1 °C cooler
Monthly sea surface temperatures

The SST anomaly map for July shows the equatorial Pacific cooled compared to the preceding month. July SSTs were warmer than average in the eastern tropical Pacific east of 110°W, extending into the northern Pacific basic, and in an area of the western tropical Pacific just west of the Date Line, with warm anomalies also present to Australia’s northwest and extending into the Indian Ocean.

Click to see full-size map showing temperatures in the tropical Pacific.
Baseline period 1961–1990.
Index June July Temperature change
NINO3 +0.9 +0.7 0.2 °C cooler
NINO3.4 +0.5 +0.2 0.3 °C cooler
NINO4 +0.6 +0.4 0.2 °C cooler
5-day sub-surface temperatures

The sub-surface temperature map for the 5 days ending 24 August shows waters across parts of the western and central equatorial Pacific are warmer than average in the top 150 m. As substantial areas of the central and eastern Pacific have low data coverage, as indicated by point observations (cross markings) on the image below, other sources of sub-surface data have also been considered.

Monthly sub-surface temperatures

The four-month sequence of sub-surface temperature anomalies (to 25 August) shows warm anomalies are present in parts of the sub-surface profile in the central Pacific and just to the west of the Date Line. The sub-surface plot also shows areas of cool anomalies in the sub-surface of the far western and shallow eastern equatorial Pacific.

Southern Oscillation Index

The Southern Oscillation Index (SOI) has fallen over the past fortnight, and has remained at values around −9 over the past week. The latest approximate 30-day SOI value to 24 August is −9.3.

Trade winds

Trade winds over the equatorial Pacific have returned to average (see anomaly map for the 5 days ending 10 August). The westerly wind anomalies seen earlier in the month did not persist, which meant that further warming of ocean surface did not occur in the tropical 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 of the trade winds.

Cloudiness near the Date Line

Cloudiness near the Date Line has been below average during the past two weeks. Cloudiness has been generally below average near the Date Line since the end of July.

Cloudiness along the equator, near the Date Line, is an important indicator of ENSO conditions, as it typically increases (negative OLR anomalies) near and to the east of the Date Line during El Niño and decreases (positive OLR anomalies) during La Niña.

Model outlooks

The international climate models surveyed by the Bureau have generally eased their forecasts slightly, with around half of the models indicating the possibility of El Niño during either late spring or early summer. The majority of surveyed models indicate that any event would be unlikely to reach far past borderline SST values.

Click to see full-size map of NINIO3.4 SST plumes from POAMA forecasts, updated daily.
Indian Ocean Dipole

The values of the Indian Ocean Dipole (IOD) index have declined over the past two weeks, but remain within negative territory. The latest weekly index value to 24 August is −0.5 °C. 2014 has been declared an IOD negative year as values of the IOD index have remained negative since mid-June.

Waters to the south of Indonesia are warmer than average while sea surface temperatures in parts of the Arabian Sea are cooler than average. Climate models surveyed in the model outlooks favour a return to neutral IOD values over the coming month. Typical evolution of IOD events sees a return to neutral conditions by the end of spring or start of summer.

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