El Niño gone by mid winter


The current El Niño episode in the Pacific is weakening and is expected to have departed by mid-winter, according to NIWA senior climate scientist Dr Jim Salinger.

"The El Niño of the past year peaked in summer and is now weakening in the eastern tropical Pacific" he said. "All evidence is now pointing to the current episode ending mid-winter."

In terms of New Zealand climate, this means a break from the persistent westerly and southwesterly winds which produced drought in northern and eastern areas of New Zealand.

"Studies of similar periods in the past when El Niño breaks down show that there is a 50:50 chance that wet easterlies will bring drought breaking rainfall to those areas still in agricultural drought (Gisborne, Hawke’s Bay, eastern Marlborough to Christchurch) by the end of April."

"The scientific evidence now coming in shows that equatorial ocean temperatures in the El Niño "warm pool" have decreased from + 5°C above normal in early December to +3°C above normal by the beginning of March. Average to above average summer rainfall occurred over the eastern half of Australia, and sea temperatures have now become warm in the Tasman and around New Zealand. All these factors normally occur when El Niño is on the decline" said Dr Salinger.

Further evidence is provided by climate prediction models that attempt to predict tropical atmospheric and oceanic changes. Most of the overseas models are in good agreement that El Niño conditions will end during winter.

"How the El Niño/Southern Oscillation (ENSO) system evolves later in the year will have a significant effect on New Zealand climate" said Dr Salinger. "At this stage where ENSO will go is unclear. The climate models give a range of outlooks and these are all rather uncertain. Firmer predictions for next summer should be possible around May."

The next few months will be critical in the future development of ENSO. The climate conditions in the tropical Pacific, and elsewhere will be closely monitored by scientists at the National Institute of Water and Atmospheric Research.



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Archived on 15 April 2019