Australia Issues La Nina Watch as Pacific Continues to Cool

(Bloomberg) -- The chances of La Nina weather conditions developing late this year have increased to at least 50 percent as the Pacific Ocean cools, Australia’s Bureau of Meteorology said as it issued a watch for the event.

While the El Nino Southern Oscillation is currently neutral, models suggest the tropical Pacific will continue to cool, the bureau said Tuesday on its website. Seven of eight climate models suggest sea surface temperatures will reach or exceed La Nina thresholds by next month, it said.

Australia’s weather bureau joins the U.S. in posting a watch for La Nina, a cooling of the Pacific that can trigger weather changes worldwide. The U.S. Climate Prediction Center says there’s a 67 percent chance for a weak La Nina some time from December to February. Prices for key agricultural commodities including corn, soy and wheat may benefit if the weather curbs production, BMI Research said last week.

“Following a brief period of warming, tropical Pacific surface waters cooled significantly in the past fortnight, and hence the central to eastern tropical Pacific Ocean is now generally cooler than average,” the weather bureau said. Atmospheric indicators including the Southern Oscillation Index, trade winds and cloudiness near the dateline are also approaching La Nina levels, it said. 

Indicators need to remain at La Nina levels for at least three months to be considered an event and this is forecast by six of the eight models, according to the weather bureau. If a La Nina does occur this year, it is likely to be short and weak as sea surface temperatures are forecast to warm again in early 2018, it said.

While La Nina events typically bring wetter conditions to eastern Australia during late spring and summer, other climate drivers including weak warm waters to the north of Australia and cooler waters in the eastern Indian Ocean mean widespread rainfall across the country between November and January isn’t favored. Weak La Nina events in Australia’s summer can also produce heatwaves in the southeast.

--With assistance from Rebecca Keenan

To contact the reporter on this story: Phoebe Sedgman in Hong Kong at psedgman2@bloomberg.net.

To contact the editors responsible for this story: Phoebe Sedgman at psedgman2@bloomberg.net, Andrew Hobbs, James Poole

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