A mature and strong El Niño is now present in the tropical Pacific Ocean and is likely to strengthen further. This year’s El Niño event is the strongest since 1997-1998 and is potentially among the four strongest events since 1950, according to the latest Update from the World Meteorological Organization.
The peak strength of this El Niño, expected sometime during October 2015 to January 2016. Its impacts are already evident in some regions and will be more apparent for at least the next 4-8 months.
“Compared to the last major El Niño event in 1997-1998, there is much more information available,” said Maxx Dilley, Director of WMO’s Climate Prediction and Adaptation Division. “We have better models and are much more prepared.”
“It is a test case for the early warning systems and climate information systems of WMO Members and we are hoping that will be of assistance to some of the affected countries,” Mr Dilley told a press conference.
The El Niño/Southern Oscillation is one of the main drivers of the climate system. and contributes to extreme events like droughts and flooding in different parts of the world. Globally, it has a warming influence on average temperatures.
Ahead of the full onset of this year’s El Niño, 2014 was nominally the warmest on record, with record ocean heat and high land-surface temperatures. This trend has continued in the first seven months of 2015, which have witnessed many extreme events ranging from devastating flooding to extreme heat and drought.
No two El Niño events are the same, and other climate phenomena also play a role. The inter-play between ENSO and climate change is the subject matter of concerted research.
David Carlson, Director of the WMO co-sponsored World Climate Research Programme, said that the 2015 El Niño is the first to take place since the rapid melting of Arctic sea ice and snow cover.
"The last big El Niño was 1997-1998. The planet has changed a lot in 15 years,” said Mr Carlson. “We have had years of record Arctic sea ice minimum. We have lost a massive area of northern hemisphere snow cover, probably by more than 1 million square kilometers in the past 15 years. We are working on a different planet and we fully do not understand the new patterns emerging."
He said the 2015 El Niño is unique because of the unprecedented combination of the Equatorial influence of El Niño, and the Arctic influence of low sea ice and snow cover in place at the same time.
"This is a new planet. Will the two patterns reinforce each other or cancel each other? We have no precedent. Climate change is increasingly going to put us in this situation. We don’t have a previous event like this," he said.
Typically, because of the warm air is over the eastern pacific, there are drier conditions over Australia, Indonesia and Southeast and South Asia. Many countries in the region are actively preparing for drought.
This year’s El Niño has also impacted the South Asian monsoon. The India Meteorological Department, for the first time in its history, gave a public drought forecast predicting monsoon rainfall 12 percent below normal, in which the early predictions of El Niño played a crucial role.
“We are seeing that Indian monsoon right now is almost 12 percent below normal. There is only a month left of the summer monsoon season making it difficult to recover,” said WMO’s El Niño expert Rupa Kumar Kolli.
“That was the kind of early warning information we can extract from the El Niño signal and it helps policy makers to prepare,” he said.
Very often during an El Niño, the Horn of Africa gets increased precipitation and sometimes flooding, whereas in southern Africa there are often get drier conditions.
From Central America to the northeastern parts of South America it is often dry. The western coast of South America is more likely to be wetter than normal. Countries in the region are making contingency plans and mobilizing disaster preparedness teams.
Typically, strong El Niño events bring winter rains to California. However, WCRP’s David Carlson said it was unclear whether this year’s event would actually break the persistent ridge that has brought drought to California.
During El Niño events, sea temperatures at the surface in the central and eastern tropical Pacific Ocean become substantially higher than normal. The WMO Update said that surface water temperatures in the east-central tropical Pacific Ocean are likely to exceed 2° Celsius above average – well above the El Niño threshold of 1° C.
The El Niño Update is available here
WMO brochure on El Niño/Southern Oscillation is available here