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

El Niño remains possible in 2014

Issued on Tuesday 9 September 2014 |

Despite some warming of the tropical Pacific Ocean over the past month, ENSO remains neutral. However, models continue to suggest an El Niño remains possible in 2014, and hence the Bureau’s ENSO Tracker remains at WATCH status, indicating at least double the normal risk of an El Niño developing by the end of the year.

Although tropical Pacific Ocean surface temperatures are within neutral range, an area of the sub-surface is warmer than average. A late season El Niño remains possible if these warmer waters rise to the surface and then affect atmospheric circulation, or if another sustained westerly wind burst develops in the western Pacific.

The majority of international climate models surveyed by the Bureau indicate central tropical Pacific surface temperatures will remain warmer than average, and may exceed El Niño thresholds by the end of the year. These model outlooks and current observations mean the Bureau’s ENSO Tracker remains at WATCH status, indicating at least a 50% chance (double the normal likelihood) of an El Niño forming in 2014.

El Niño is often associated with below-average rainfall over large parts of southern and eastern inland areas of Australia and above-average daytime temperatures over southern Australia. Such impacts can often occur while an event is developing, as experienced in some locations over the past several months.

The negative Indian Ocean Dipole (IOD) in the tropical Indian Ocean has shown signs of weakening. Waters to the north of Australia and in the Timor Sea have cooled over the past two weeks. All climate models surveyed by the Bureau indicate the IOD will continue to weaken, with neutral conditions likely to return during the austral spring.

Next update expected on 23 September 2014 | print version

Weekly sea surface temperatures

Sea surface temperature (SST) anomalies across the tropical Pacific remain similar to two weeks ago. Positive anomalies are present along most of the equatorial Pacific, although positive anomalies are patchy in the central Pacific (see SST anomaly map for the week ending 7 September). Warm anomalies also remain in areas of the southeastern Indian Ocean and across most of the northern Pacific Basin. In the past fortnight, some cool anomalies have emerged around northern Australia, including parts of the Timor Sea. Cool temperatures in these areas are less favourable for rainfall over Australia.

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 +0.4 0.1 °C cooler
NINO3.4 +0.3 +0.3 no change
NINO4 +0.6 +0.6 no change
Monthly sea surface temperatures

The SST anomaly map for August shows the equatorial Pacific cooled somewhat around 120°W in the eastern Pacific and warmed across the western Pacific when compared to the preceding month. August SSTs were near-average across much of the central tropical Pacific and warmer than average elsewhere across the tropics, extending into the northern Pacific basic 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 July August Temperature change
NINO3 +0.7 +0.5 0.2 °C cooler
NINO3.4 +0.2 +0.3 0.1 °C warmer
NINO4 +0.4 +0.7 0.3 °C warmer
5-day sub-surface temperatures

The sub-surface temperature map for the 5 days ending 7 September shows parts of the central and eastern equatorial Pacific are 2–3 °C warmer than average around 100 m depth. 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 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) fell slightly during the past fortnight before returning to values around −9. The latest approximate 30-day SOI value to 7 September is −9.7.

Trade winds

Trade winds over the equatorial Pacific are near-average (see anomaly map for the 5 days ending 7 September).

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 fluctuated around average during the past two weeks. Until recently cloudiness near the Date Line had been generally below average 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

Most international climate models surveyed by the Bureau indicate the possibility of El Niño thresholds being reached by early summer, although two indicate persistence of neutral SST values in the central equatorial Pacific. Two models indicate ocean temperatures may reach moderate El Niño levels, while all others favour borderline SST values. This would tend to suggest any event is likely to be relatively weak.

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

The Indian Ocean Dipole (IOD) index rose to −0.2 °C last week, but has moved back past the negative threshold value this week. The latest weekly index value to 7 September is −0.7 °C.

Waters to the south of Indonesia remain warmer than average with near-average sea surface temperatures in the Arabian Sea. However closer to Australia, waters in the Timor Sea are now near-average to cooler than average, as are sea surface temperatures around the northern Australian coasts. Climate models surveyed in the model outlooks favour a return to neutral IOD values during September. 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.