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Negative IOD continues as tropical Pacific remains ENSO neutral

La Niña Alert ENSO

The tropical Pacific Ocean remains El Niño–Southern Oscillation (ENSO) neutral. Negative Indian Ocean Dipole (IOD) conditions continue, but are likely to ease by the end of spring.

Trade winds in the tropical Pacific have returned to near-average after a surge in early October. Correspondingly, sea surface temperatures (SSTs) in the central tropical Pacific Ocean cooled, but then rebounded, and remain within the ENSO neutral range.

In the atmosphere, the Southern Oscillation Index (SOI) has returned to near-zero values. However, cloudiness near the Date Line continues to reflect a La Niña-like pattern.

Most climate models predict SSTs will remain cooler than average, but ENSO-neutral, through until the end of the 2016–17 summer. Only two of eight models suggest brief, weak La Niña levels may occur towards the end of 2016. The ENSO Outlook remains at La Niña WATCH.

Warmer than average sea surface temperatures to Australia’s north suggest that some La Niña-like impacts are likely, even if an event never fully develops.

The negative IOD event, which has been in place since late May, persists. Warming of SSTs east of tropical Africa has seen IOD index values weaken over the past month, but SSTs remain very much warmer than average south of Indonesia.

Models indicate the IOD will return to neutral by the end of spring. Both a negative IOD and La Niña typically contribute to increased rainfall in spring for eastern and central Australia.