(Adds S&P agricultural index in final paragraph.)
June 3 (Bloomberg) -- An El Nino weather pattern may be established by August as Australia remains on alert for the event that brings drought to the Asia-Pacific region and heavier-than-usual rains to South America.
The alert indicates at least a 70 percent chance of an El Nino developing in 2014, the Bureau of Meteorology said on its website today. Just over half of the climate models surveyed suggest the event will become established by August, it said.
Forecasters from the U.S. to the United Nations have warned an event may happen this year, and ABN Amro Group NV said confirmation could spur support for coffee, sugar and cocoa prices. El Ninos can roil agricultural markets worldwide as farmers contend with drought or too much rain. The chance of a weak event is 65 percent, according to Commodity Weather Group LLC, while AccuWeather Inc. puts the odds at 80 percent.
“It is not uncommon to see some impacts prior to an event becoming fully established,” the bureau said. “May rainfall was below normal across parts of eastern Australia and maximum temperatures were above normal across much of the south and east.”
Most international climate models indicate that sea surface temperatures in the equatorial Pacific Ocean are likely to continue to warm during winter, according to the bureau. While several have eased their predictions slightly, around half continue to indicate that the equatorial Pacific is likely to exceed El Nino thresholds before or during the southern hemisphere spring, it said.
El Ninos, caused by the periodic warming of the tropical Pacific, occur irregularly every two to seven years and are associated with warmer-than-average years. The last El Nino was from 2009 to 2010, and since then the Pacific has either been in its cooler state, called La Nina, or neutral.
A weak El Nino is more likely because of the weakening of the warm pool of water below the surface of the Pacific Ocean and “the difficulty in getting the trade winds to weaken significantly,” David Streit, co-founder of Bethesda, Maryland- based CWG, said in an e-mail to Bloomberg.
The pattern will probably set in during July and last six to eight months, and may be of weak to moderate intensity, according to Dale Mohler, a forecaster at AccuWeather. The probability of an El Nino is about 85 percent and it should develop by late June, said Donald Keeney, a meteorologist at MDA Weather Services in Gaithersburg, Maryland, who predicts a 35 percent chance of weak pattern.
Trade winds are near-average across the tropical Pacific, according to the Australian weather bureau.
While the Standard & Poor’s GSCI index of eight agricultural commodities climbed 10 percent this year, it’s declined 8.8 percent from an 11-month high at the start of May on signs of increasing world grain supplies.
--With assistance from Diep Ngoc Pham in Hanoi.