'Substantial' El Nino event predicted

Helen Briggs BBC 12 May 15;

The El Nino effect, which can drive droughts and flooding, is under way in the tropical Pacific, say scientists.

Australia's Bureau of Meteorology predicted that it could become a "substantial" event later in the year.

The phenomenon arises from variations in ocean temperatures.

The El Nino is still in its early stages, but has the potential to cause extreme weather around the world, according to forecasters.

US scientists announced in April that El Nino had arrived, but it was described then as "weak".

Australian scientists said models suggested it could strengthen from September onwards, but it was too early to determine with confidence how strong it could be.

"This is a proper El Nino effect, it's not a weak one," David Jones, manager of climate monitoring and prediction at the Bureau of Meteorology, told reporters.

"You know, there's always a little bit of doubt when it comes to intensity forecasts, but across the models as a whole we'd suggest that this will be quite a substantial El Nino event."

An El Nino comes along about every two to seven years as part of a natural cycle.

Every El Nino is different, and once one has started, models can predict how it might develop over the next six to nine months, with a reasonable level of accuracy.

A strong El Nino five years ago was linked with poor monsoons in Southeast Asia, droughts in southern Australia, the Philippines and Ecuador, blizzards in the US, heatwaves in Brazil and extreme flooding in Mexico.

Another strong El Nino event was expected during last year's record-breaking temperatures, but failed to materialise.
Prof Eric Guilyardi of the Department of Meteorology at the University of Reading said it would become clear in the summer whether this year might be different.

"The likelihood of El Nino is high but its eventual strength in the winter when it has its major impacts worldwide is still unknown," he said.

"We will know in the summer how strong it is going to be."

Weather patterns

The El Nino is a warming of the Pacific Ocean as part of a complex cycle linking atmosphere and ocean.

The phenomenon is known to disrupt weather patterns around the world, and can bring wetter winters to the southwest US and droughts to northern Australia.

The consequences of El Nino are much less clear for Europe and the UK.

Research suggests that extreme El Nino events will become more likely as global temperatures rise.

How can we predict El Nino?

In the tropical Pacific Ocean, scientists operate a network of buoys that measure temperature, currents and winds. The data - and other information from satellites and meteorological observations - is fed into complex computer models designed to predict an El Nino. However, the models cannot predict the precise intensity or duration of an El Nino, or the areas likely to be affected. Researchers are trying to improve their models to give more advance notice.

El Nino will be 'substantial', warn Australian scientists
AFP By Madeleine Coorey Yahoo News 12 May 15;

Australian scientists on Tuesday forecast a "substantial" El Nino weather phenomenon for 2015, potentially spelling deadly and costly climate extremes, after officially declaring its onset in the tropical Pacific.

El Nino had been expected last year when record-breaking temperatures made 2014 the hottest in more than a century. The Australian Bureau of Meteorology said while the thresholds were not met until now it was expected to be a significant event.

The Japan Meteorological Agency also confirmed the phenomenon had begun and forecast it would continue into late 2015.

"There's always a little bit of doubt when it comes to intensity forecasts, but across the models as a whole we'd suggest that this will be quite a substantial El Nino event," David Jones, from the bureau's climate information services branch said.

"Certainly the models aren't predicting a weak event. They are predicting a moderate-to-strong El Nino event. So this is a proper El Nino event, this is not a weak one or a near miss as we saw last year."

The El Nino phenomenon -- which is associated with drought conditions in Australia -- can cause havoc for farmers and global agricultural markets, hitting economies heavily dependent on the land.

The last El Nino five years ago had a major impact with monsoons in Southeast Asia, droughts in southern Australia, the Philippines and Ecuador, blizzards in the United States, heatwaves in Brazil and killer floods in Mexico.

It occurs when the trade winds that circulate over waters in the tropical Pacific start to weaken and sea surface temperatures rise.

- Severe drought -

US officials announced earlier this year that the long-awaited El Nino had arrived, but the National Oceanic and Atmospheric Administration described it as of "weak strength".

Australian scientists said models were now showing it was likely to see an increased intensity from about September and have potential global impacts.

"Last year we saw some indices, such as the sea surface temperatures at times exceed El Nino thresholds... but we didn't see them all coming together at the same time or we didn't see it sustained," Jones explained.

He said this year's pattern could create drier conditions in Indonesia, Papua New Guinea and parts of Southeast Asia.

In the past it has caused heavier-than-normal rainfall in the eastern Pacific and South America -- raising the spectre of floods and landslides, while the southwest United States and southern Africa tend to be drier.

An El Nino is potentially a bad sign for large swathes of Australia, including the states of Queensland and New South Wales, which are already in the grip of severe drought.

Neil Plummer, the bureau's assistant director for climate information services, said it was often associated with below average rainfall across eastern Australia and warmer temperatures in the southern half over the hottest months.

"The onset of El Nino in Australia in 2015 is a little earlier than usual," he said, adding that this was the first such phenomenon in the tropical Pacific since March 2010.

"Prolonged El Nino-like conditions have meant that some areas are more vulnerable to the impact of warmer temperatures and drier conditions."

El Nino is forecast to strengthen during the southern hemisphere winter but while the event increases the risk of drought, it does not guarantee it -- with only 17 of the 26 El Nino events since 1900 resulting in widespread drought in Australia.

On the upside, the bureau said it would expect the tropical cyclone season to be below average for Australia.

"Every El Nino is different and we know that some years like 1972, 1982 and 1994 really fit the stereotype strongly, severe drought, very hot daytime temperatures, bushfire activity and so on," said Jones.

"But not every El Nino event follows that pattern."