The sea-surface temperature (SST) anomaly map for March shows warm anomalies have emerged along the equator in parts of the eastern Pacific, replacing cool anomalies which were present during February. Warm anomalies in the western Pacific and around Australia’s north and west have weakened while warm anomalies to Australia’s south have strengthened, particularly in the southeast; surface waters in these areas are generally more than 1 °C warmer than average. Broadly, the tropical Pacific Ocean remains close to the long term average.

Baseline period 1961–1990. Index February March Temperature change NINO3 −0.3 +0.3 0.6 °C warmer NINO3.4 −0.2 +0.1 0.3 °C warmer NINO4  0.0  0.0 no change

SST anomalies have cooled slightly across all three monitored NINO indices compared to two weeks ago. The pattern of SST anomalies across the Pacific Basin remains generally similar although cool anomalies along the South American coastline have decreased in strength. The map for the week ending 21 April shows SSTs along the equator are mostly near average for this time of the year with weak warm anomalies in the far western Pacific. Warm anomalies remain around much of the Australian coastline, and have strengthened during the past two weeks.

Baseline period 1961–1990. Index Previous Current Temperature change (2 weeks) NINO3 +0.3 +0.2 0.1 °C cooler NINO3.4 +0.2 +0.1 0.1 °C cooler NINO4 +0.1  0.0 0.1 °C cooler

An animation of recent SST changes | Weekly data graph | Map of NINO regions

Compared to two weeks ago, the sub-surface map for the 5 days ending 21 April shows cool anomalies in the subsurface of the eastern Pacific have strengthened; water more than 1 °C cooler than average is present between 50 and 250 m deep across nearly all of the equatorial Pacific. Warm anomalies are still present in the far western equatorial Pacific sub-surface, but have weakened slightly compared to two weeks ago.

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

The Southern Oscillation Index (SOI) has dropped slightly compared to two weeks ago. The latest 30-day SOI value to 21 April is +6.9.

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 across the western tropical Pacific during the past two weeks. The anomaly map for the 5 days ending 21 April shows trade winds are stronger than average across the western half of the tropical Pacific and near average elsewhere.

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 has been slightly below average during the past two weeks. There has not been a sustained deviation in cloudiness since March 2012, coinciding with the close of the most recent La Niña event.

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.

International climate models surveyed by the Bureau indicate that SSTs in the equatorial Pacific Ocean are expected to remain neutral at least through the southern hemisphere winter. Predictions from dynamical models are known to have lower skill during the April to June period, however, all surveyed models are consistent in their outlooks.

The Indian Ocean Dipole (IOD) is currently neutral, with the latest IOD index value at +0.1 °C for the week ending 21 April. Current model outlooks indicate the IOD will remain on the cool side of neutral into the southern hemisphere winter. However, two of the five models surveyed indicate the possibility of a negative IOD heading into the southern spring. A negative IOD during spring increases the chances of above normal rainfall over southern Australia.

IOD time series IOD map IOD forecasts DMI values