Nov 7 2014

Meteorologist explains El Niño, likely to develop this winter

Republished with permission of SEAFOODNEWS.COM November 6, 2014
In 1997-1998 abnormally high ocean temperatures off South America caused a collapse of the anchovy fisheries. Anchovies are a vital link in the food chain, and shortages can bring great hardship. Weather extremes associated with the event caused 2,000 deaths and $33 million (€26 million) in property damage. One commentator wrote that the warming event had “more energy than a million Hiroshima bombs”.

As it is not uncommon for an ocean warming to commence around Christmas, the fisherman of Peru call it El Niño, the Christ child. El Niño occurs when the temperature of the equatorial ocean west of South America is above normal, but its effects are more widespread.

Weather patterns in Indonesia and Australasia and the monsoons of southern Asia are affected. East Africa and North America also feel its impact. The heavy rainfall of Indonesia ceases, and droughts and wildfires are common in southeast Asia and Australia. Meanwhile, the mid- Pacific suffers a deluge.

During El Niño, the trade winds – which normally blow towards the west – weaken, allowing warm water from the western Pacific to slosh eastwards. El Niño lasts from a few months to a year or more and occurs about twice each decade, but its period is very irregular. It is linked to a see-saw pattern in which pressure in Tahiti is high when it is low in Darwin and vice versa. Together, this gives us Enso (El Niño southern oscillation).

Since February of 2014, some atmospheric models have been predicting the onset of El Nino, but it never quite materializes.

At the moment, there is evidence of warming along the South American Pacific coast, but that has not yet reached El Nino thresholds, despite disrupting the anchovy fisheries.

The current NOAA forecast says “Similar to last month, most models predict El Niño to develop during October-December 2014 and to continue into early 2015. However, the ongoing lack of clear atmosphere-ocean coupling and the latest NCEP CFSv2 model forecast have reduced confidence that El Niño will fully materialize. If El Niño does emerge, the forecaster consensus favors a weak event. In summary, there is a 58% chance of El Niño during the Northern Hemisphere winter, which is favored to last into the Northern Hemisphere spring 2015.

In Australia the Bureau of Meteorology says  “Weather conditions similar to El Nino will continue amid warming of the Pacific Ocean as thresholds for the event that brings drought to Asia and heavier-than-usual rains to South America may be reached by early next year.

Three of eight climate models may reach El Nino thresholds in January and another two remain just shy of the levels, the Australia’s Bureau of Meteorology said on its website today, maintaining an Oct. 21 outlook. The forecaster kept a watch status, indicating at least a 50 percent chance of a weak to moderate event, it said.

The bureau has pushed back projections for the onset of El Nino as changes to the atmosphere have failed to develop consistently. A weak event will probably develop by year end, MDA Weather Services predicted last month. El Ninos can roil agricultural markets as farmers contend with drought or too much rain. Palm oil, cocoa, coffee and sugar are among crops most at risk, Goldman Sachs Group Inc. has said.

“Sea surface temperatures in the tropical Pacific Ocean have warmed over the past two months, and the Southern Oscillation Index has remained negative, but indicators generally remain in the neutral range,” the bureau said. “The existence of warmer-than-average water in the tropical Pacific sub-surface supports a continuation of the current near-El Nino conditions.”

While sea-surface temperatures are warmer than normal across most areas in the tropical Pacific ocean, it still doesn’t qualify as an El Nino, Kyle Tapley, senior agricultural meteorologist at MDA said in response to e-mailed questions. Some additional warming could lead to the development of a weak El Nino, he said.

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