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

El Niño likely in 2014

Issued on Tuesday 22 April 2014 |

The likelihood of El Niño remains high, with all climate models surveyed by the Bureau now indicating El Niño is likely to occur in 2014. Six of the seven models suggest El Niño thresholds may be exceeded as early as July.

The Pacific Ocean has been warming along the equator over recent weeks, with continued warming in the central Pacific likely in coming months. Another burst of westerly winds is presently occurring in the western Pacific, and is likely to cause further warming of the sub-surface.

El Niño has an impact across much of the world, including below average rainfall in the western Pacific and Indonesian regions, and increased rainfall in the central and eastern Pacific. For Australia, El Niño is usually associated with below average rainfall, with about two thirds of El Niño events since 1900 resulting in major drought over large areas of Australia.

The Indian Ocean Dipole (IOD) is currently in a neutral state. Model outlooks currently suggest the IOD is likely to remain neutral through late autumn and early winter, with two of the five models surveyed suggesting a positive IOD may develop by early spring. Positive IOD events often coincide with El Niño and are typically associated with large parts of southern and central Australia experiencing lower rainfall than usual.

Next update expected on 6 May 2014 | print version

Monthly sea surface temperatures

Compared to February, the equatorial Pacific has warmed over the past month. The sea surface temperature (SST) anomaly map for March shows that much of this region is now near average to warmer than average, while in February cool anomalies dominated along the equator in the east.

Click to see full-size map showing temperatures in the tropical Pacific.
Baseline period 1961–1990.
Index February March Temperature change
NINO3 −0.5 +0.1 0.6 °C warmer
NINO3.4 −0.3 0.0 0.3 °C warmer
NINO4 +0.4 +0.6 0.2 °C warmer
Weekly sea surface temperatures

The SST anomaly map for the week ending 20 April is similar to that of two weeks ago, with warm temperature anomalies along the equator covering most of the central Pacific and nearly the entire eastern Pacific. The current pattern of warm anomalies has been developing over the past two months and is consistent with a developing El Niño.

Waters surrounding Australia are generally warmer than average, except for the northeast region.

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 +0.5 +0.4 0.1 °C cooler
Monthly sub-surface temperatures

The four-month sequence of sub-surface temperature anomalies (to 21 April) shows waters are warmer than average across most of the sub-surface of the equatorial Pacific. The sequence over recent months shows the development and eastward migration of this pool of warmer than average water. Water at around 100 m depth between 160°W and 130°W has reached more than 4 °C warmer than average.

Weekly sub-surface temperatures

The sub-surface temperature map for the 5 days ending 20 April shows water in the sub-surface of the equatorial Pacific is generally warmer than average in the top 200 m. Water in an area of the sub-surface in the central equatorial Pacific has reached more than 3 °C above average around 150 m, while warmer anomalies in excess of 5 °C above average are present near the surface of the far eastern equatorial Pacific.

The animation of sub-surface temperature changes shows the progression of the warmer waters across the Pacific (which is known as a Kelvin wave). Downwelling Kelvin wave events are driven by westerly winds over the western tropical Pacific. This pool of warmer-than-average sub-surface water is expected to cause a further warming at the surface of the central and eastern tropical Pacific, and hence contribute to the formation of an El Niño during winter.

Southern Oscillation Index

The Southern Oscillation Index (SOI) has risen to neutral values over the past two weeks after a prolonged period of falling values. The latest approximate 30-day SOI value to 20 April is +2.2.

Sustained positive values of the SOI above +8 may indicate a La Niña event, while sustained negative values below −8 may indicate an El Niño event. Values of between about +8 and −8 generally indicate neutral conditions.

Trade winds

Westerly wind anomalies are present over the western half of the equatorial Pacific, while trade winds are near-average along the equator in the eastern tropical Pacific (see anomaly map for the 5 days ending 20 April).

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 generally been above average since late February.

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 an El Niño event and decreases (positive OLR anomalies) during a La Niña event.

Model outlooks

All international climate models surveyed by the Bureau indicate that SSTs in the equatorial Pacific Ocean are likely to continue to warm into winter. All models indicate that the equatorial Pacific is likely to exceed El Niño thresholds by the southern hemisphere spring, with six of seven models expecting this to occur by July.

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

The Indian Ocean Dipole (IOD) remains neutral, with the latest weekly index value (20 April) 0.0 °C.

Climate models surveyed in the model outlooks favour neutral IOD values over the coming months. However, the development of an El Niño would increase the chance of a positive IOD event two models indicate this is a possibility by early spring. Positive IOD events often coincide with El Niño and are typically associated with lower than average winter and spring rainfall over parts of southern and central Australia.

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