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 general distribution of warm and cool sea-surface temperature (SST) anomalies across the tropical Pacific Ocean remain similar to that of two weeks ago, although warm anomalies in the far eastern Pacific have decreased in both extent and intensity. Two of the three NINO indices monitored have warmed slightly over the past two weeks, with the third remaining unchanged; all three are within neutral values. The SST anomaly map for the week ending 6 May shows the sea-surface temperature across most of the equatorial Pacific is near average for this time of the year. However, there are warm anomalies in the far western and eastern Pacific as well as south of the equator, and an area of cool anomalies north of the equator in the central Pacific. Across most of their area, these anomalies are less than one degree above or below average.

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

An animation of recent SST changes | Weekly data graph

Over the past fortnight the volume of cooler-than-average water in the sub-surface of the central and eastern equatorial Pacific has continued to decrease. Generally, water in the shallow sub-surface is slightly warmer than usual across the equatorial Pacific, and near average at depth. The map for the 5 days ending 6 May shows 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 continued rising during the past week, after remaining around −7 during the preceding week. The latest (6 May) 30-day SOI value is +0.7.

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 over most of the tropical Pacific during the past two weeks. Trade winds are generally near normal over the tropical Pacific (see wind anomaly map for the 5 days ending 6 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, increasing again over the past two weeks, but generally remaining 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.

All outlooks from leading international climate models surveyed by the Bureau indicate neutral ENSO conditions are the most likely scenario for the remainder of autumn. While most models note a heightened risk of El Niño conditions emerging during late winter or spring, other models forecast neutral conditions to continue during this period.

The IOD index is currently neutral, with a value of −0.3 for the week ending 6 May.

Recent forecasts from the POAMA model predict neutral IOD conditions for the remainder of autumn and the following winter.

IOD time series IOD map IOD forecasts DMI values