Sea surface temperature (SST) in the central and eastern equatorial Pacific Ocean continued to warm during April. The SST anomaly map for April shows SSTs were near normal across most of the tropical Pacific. While still present, the area of slightly cool anomalies north of the equator has decreased substantially when compared to the map for March. Warm anomalies in the far eastern Pacific, near the equator and along the South American coast, have increased in extent and strength over the past month, with a small area of ocean more than 2 °C warmer than usual.

Index March April Temperature change NINO3 +0.1 +0.3 0.2 °C warmer NINO3.4 −0.3 −0.2 0.1 °C warmer NINO4 −0.4 −0.1 0.3 °C warmer

The distribution of warm and cool sea-surface temperature (SST) anomalies across the tropical Pacific Ocean remains similar to that of two weeks ago, and generally has moved closer to normal values for this time of year − weak warm anomalies south of the equator in the central and eastern Pacific have decreased in extent, as have warm anomalies north of Indonesia. The SST anomaly map for the week ending 20 May shows an area of weak cool anomalies remains north of the equator in the central Pacific, although sea-surface temperatures across most of the equatorial Pacific are near average for this time of the year.

Index Previous Current Temperature change (2 weeks) NINO3 +0.3 +0.3 no change NINO3.4 +0.1 −0.1 0.2 °C cooler NINO4 −0.1 −0.1 no change

An animation of recent SST changes | Weekly data graph

When compared with two weeks ago, the map for the 5 days ending 20 May shows the distribution and strength of subsurface temperature anomalies in the equatorial Pacific remains largely unchanged. Most of the water in the shallow sub-surface is slightly warmer than usual across the equatorial Pacific, with the focus of warm anomalies being somewhat deeper in the west, and slightly below average at depth. There are volumes of water more than 2 °C warmer than usual in both the western and far eastern equatorial Pacific.

Animation of recent sub-surface changes | Archive of sub-surface temperature charts

The Southern Oscillation Index (SOI) has remained within neutral values over the past two weeks, rising to +5.5 before falling again. The latest (20 May) 30-day SOI value is +0.2.

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.

Monthly_graph | SOI table | SOI text

Trade winds have weakened slightly over the western and central tropical Pacific during the past two weeks. Trade winds are generally near normal over the tropical Pacific, while there are westerly winds present over the Maritime Continent (see wind anomaly map for the 5 days ending 20 May).

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 continues to fluctuate, but generally remains close to average.

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.

While all international climate models surveyed by the Bureau indicate neutral ENSO conditions are expected for early winter, most models forecast that the Pacific is likely to reach El Niño conditions before the end of spring.

The IOD is currently neutral, with an index value of +0.6 for the week ending 20 May.

Recent forecasts from the POAMA model predict neutral IOD conditions for winter and spring.

IOD time series IOD map IOD forecasts DMI values