La Nina’s return raises chance for disruptive crop weather

La Ninas, which are the cooling of the ocean near South America, tend to bring dry conditions to Argentina and the U.S. southern plains. They tend to deliver excess moisture to Australia.

If that sounds familiar, it’s because there was a La Nina last fall. The system helped knock down U.S. hard winter wheat production by 23 percent from the previous year and Argentine soybean production by 10 percent. The drought in Texas and Oklahoma forced producers to deeply cull their cattle herds, raising the expectations for more record beef prices in 2012.

It helped produce a December deluge in eastern Australia that ruined grain quality.

It was weakening this year and by early summer it appeared we might be entering a neutral period with neither a La Nina nor an El Nino.

But it is becoming clear that a La Nina is reforming.

The U.S. Climate Prediction Center and Australia’s weather bureau both say predictive models show the La Nina will likely strengthen and continue into the northern hemisphere’s 2012 spring.

Right now it is weaker than it was at the same time last year, and forecasts suggest it won’t become as strong as last year’s event, which was the second strongest since record keeping began in 1879.

But it is already affecting South American crops. The dryness in Argentina has caused the agriculture department to forecast 2011-12 wheat production at 11 to 13 million tonnes, down from 14.7 million tonnes last year.

But rain arrived in early October, which should stop the deterioration as farmers begin the wheat harvest.

There is no official Argentine soybean forecast, but the U.S. Department of Agriculture forecasts 53 million, up from last year’s 49 million. Rabobank thinks the dry weather will shave production to 51 million tonnes.

The threat of dry weather has caused Brazil’s crop supply agency Conab to use normal yields in its first forecast for soybean production rather than last year’s record yield, which was produced thanks to excellent rain despite the La Nina.

Applying the normal yield to the expected acreage produces a crop of 72.2 to 73.3 million tonnes, down from last year’s record 75.3 million. The USDA’s forecast is 73.5 million and Rabobank’s is 74.3 million.

After a dry September, rain was moving into Brazil’s soybean regions just as seeding was to begin, which limited the immediate threat.

As Brazil’s experience last year shows, a La Nina does not guarantee crop problems, but it increases the chance of them, depending on its strength and duration.

The La Nina effect is helping Australia’s wheat and canola crops. All areas of the country have received good rain and the country should have a near record crop as long as there is not a repeat of torrential rain and flooding.

In Western Canada, La Nina tends to deliver colder than normal winters and the potential for wet springs, just as we have had the past two years.

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