There’s little chance of La Nina fading before spring seeding, and that means likely continuing instability for southern hemisphere crops in their crucial growing seasons.
And once the northern hemisphere seeding season hits, not only will La Nina probably have an impact, but a clash between it and an arctic weather phenomenon could throw wild curve balls at North American crops, says a leading agricultural weather expert.
“That’s the impact of this high pressure block and its influence on the storm track and what could be a residual (impact) from La Nina and its usual impact on the Midwest weather impact,” said DTN meteorologist Bryce Anderson.
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The present La Nina is “moderate to strong,” according to scientific measures, and that is the cause of eastern Australia’s severe rain and flooding and Argentina’s dryness.
Both factors have become major market influences as drastic downgrading of eastern Australia’s crops have created world shortages, including malting barley.
At the same time, dry weather in central Argentina is cutting that country’s crop potential, and Anderson said those conditions could soon reach up into southern Brazil.
Wetness in eastern Australia and dryness in central Argentina are common results of La Nina, and there is no question that a La Nina is occurring, Anderson said.
The southern oscillation index, which is a measure of subsurface temperatures in a zone of the southeastern Pacific, needs to reach a reading of eight before a La Nina is declared, he said.
In December, that reading was 26.8, and in the last three months of 2010 it was an average of 20.8. That makes it a “moderate to strong” La Nina.
That helps explain the southern hemisphere problems, Anderson said, and suggests the phenomenon will survive and affect the northern hemisphere’s crops this spring and at least into the beginning of June.
Normally for North America that means dry conditions in the U.S. Midwest, which may be why the U.S. southern plains are dry and endangering winter wheat crops.
However, Anderson thinks La Nina’s usual impact will likely be rocked by the impact of an arctic weather phenomenon, which many believe caused the wet conditions on the Canadian Prairies and parts of the United States last spring and early fall.
With this “northern latitude high pressure blocking” phenomenon shoving air masses south across the plains, wild weather is likely.
It could also cause the same sort of divided Midwest U.S. growing season as last year, in which areas west of the Mississippi were unusually wet and tempestuous because of the arctic situation, but the eastern Midwest was dry due to La Nina.
“That block last summer was a big time storm producer over the western corn belt, but it really shut off once you got into the central part of Illinois,” said Anderson.
We could see that continue this summer.”
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