SYDNEY (Reuters) - The tropical Pacific Ocean has reached La Nina temperature levels, although climate models suggest the weather event will be weak and short-lived, Australian weather officials said on Tuesday.
La Nina events are triggered by a drop in sea surface temperatures in the central Pacific Ocean, generally bringing stormier, colder winters to the northern hemisphere and warmer, wet summers in the southern hemisphere.
"La Nina typically brings above-average rainfall to eastern Australia during late spring and summer," Australia's Bureau of Meteorology (BOM) said in a statement.
"However, sea surface temperature patterns in the Indian Ocean and closer to Australia are not typical of a La Nina event, reducing the likelihood of widespread above-average summer rainfall."
The increased odds for more rain in eastern Australia could further dent a wheat crop already hit by heavy weekend rain.
Australian farmers have had a tough wheat growing season, with the world's fourth-largest wheat exporter set to harvest its smallest crop in a decade after this year's severe drought reduced yields.
"The wheat growers could be the major losers if the summer rains from a La Nina eventuate," said Phin Ziebell, an agribusiness economist for National Australia Bank.
Ziebell said he had already cut his forecast for Australia’s national wheat crop this year to no more than 20 million tonnes, which would make the harvest below average.
"I’m only expecting between 18 million and 20 million tonnes, all-up this year, even before today’s announcement of La Nina. If we can get that, it would be a pretty good achievement."
La Nina is the opposite of an El Nino weather pattern, which is characterized by warmer waters in the tropical Pacific.
While a La Nina can be less damaging than an El Nino, it can cause major disruptions in grain markets, with the weather event linked to lower-than-average rainfall in North America, affecting major grain growing areas.
The BOM said climate models suggested the weather event was likely to persist over the southern summer but would be weaker than the strong La Nina of 2010–12.
Energy traders say La Niña could bring a colder-than-usual winter in the northern hemisphere, which would boost already strong demand for thermal coal and natural gas as a heating fuel.
(Reporting by James Regan and Jonathan Barrett in SYDNEY; Additional reporting by Henning Gloystein in SINGAPORE; Editing by Tom Hogue and Clarence Fernandez)
