Ag Weather Forum

North And South America Comments

Mike Palmerino
By  Mike Palmerino , DTN Senior Ag Meteorologist

As we head into the last few days of November we would like to make a few comments about the weather patterns in both South and North America.

Across South America where most of the interest is right now as it concerns developing corn and soybeans, conditions are looking pretty good. We started off the growing season in Brazil with a delay in the start of the rainy season in the Mato Grosso which delayed soybean planting. This situation continued until about the last 10 days when we have begun to see the onset of the rainy season. It is unlikely that once the rainy season is underway that any significant dryness will return during the remainder of the growing season in this region. The growing areas of Parana and Rio Grande do Sul as well as central Argentina were unfavorably wet earlier in the growing season but we have begun to see a more favorable balance between dry weather and rainfall which has favored both planting and developing corn and soybeans. These areas tend to be more vulnerable to drought during the summer but due to the fact we are in an El Nino pattern that likelihood would be diminished this year.

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The month of November was quite noteworthy across the central US with the unusual persistence of very cold weather in the Midwest. Des Moines IA experienced 252 consecutive hours of below freezing temperatures during the month of November which was the greatest in 137 years of record keeping. The most concerning aspect of this from the point of view of a meteorologist was the inability see this coming very far in advance. Once again this was all brought on by the development of blocking features (high pressure) in the high latitudes of North America. When it happens in the winter it can lead to extreme winter weather conditions in the US. When it happens in the summer it usually leads to very favorable growing conditions for corn and soybeans.

The blocking pattern at this time has shifted further to the north up to or just on the other side of the pole which has allowed the core of coldest weather to shift to the north of the border into Canada. When this happens the pattern reverts into one featuring more variable temperature (up and down). Storminess with the relaxed pattern would tend to follow more of an El Nino characteristic which would mean the most likely areas for significant precipitation would tend to favor southern and eastern areas of the US which would include the southern and eastern Midwest.

It appears to us that the blocking pattern trumps all other features that can control our weather. And when significant blocking does occur its impact on the US is significant. Unfortunately we are not in a position to have more than a 5-7 day notice from the models that a significant blocking pattern is going to develop. With that being said we would expect that additional episodes of severe winter weather are in store for us in the coming months due to the persistence of this blocking feature during the past couple of years.

Mike

(ES)

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