Sea temperatures in the tropical Pacific are just shy of La Nina thresholds and show a clear progression toward the pattern, the Bureau of Meteorology said on its website on Tuesday. Atmospheric indicators have shown signs of shifting into a La Nina-like state, it said. The bureau issued an alert, meaning an approximately 70 percent chance of the event occurring.
La Ninas occur when the atmosphere above the equatorial Pacific reacts to cooling water temperatures and typically deliver colder winters across the northern U.S., drought in Brazil’s soybean-growing areas and flooding rains across the coal-mining regions of Australia. The U.S. earlier this month
said a weak La Nina formed in October and had a 64 percent chance of lasting through March.
Australia’s weather bureau said all international climate models reach La Nina thresholds in December, with most maintaining values until at least February. Any event is likely to be weak and short-lived, it said.
Prices for agricultural commodities including corn, soybeans, wheat, cotton, sugar and coffee may rise and be volatile if La Nina arrives, BMI Research said last month. Australia’s cotton output may benefit
as the rain that the event brings can fill dams for irrigators, according to Cotton Australia.
La Nina typically causes above-average rainfall in eastern Australia during late spring and summer. However, sea surface temperature patterns in the Indian Ocean and closer to Australia are not typical of La Nina, reducing the likelihood of widespread summer rain. The pattern can also increase the likelihood of prolonged warm spells for southeast Australia.
La Nina typically brings drier conditions to the U.S. South and wetter weather to the Pacific Northwest and western Canada.
Last year's La Nina was unusually brief, forming in November and gone by February. This one should hang around through the end of winter. While it may last a bit longer than last year's La Nina, it should be just as weak, said Mike Halpert, deputy director of NOAA's Climate Prediction Center.
Copyright 2017, Bloomberg News
* with additional news from AP