South America Calling

It has been a very unusual October weather pattern in South America this year. Fronts have been very common, that isn't unusual. But they've been very strong and have been pushing much farther north than usual. That has led to long periods of dryness in central Brazil, with overall good soil moisture farther south. This continues for the first week of November, but could the pattern change after that?

During September, October and November, it is common for fronts to move through Argentina and into southern Brazil, where they usually fade out. Meanwhile, monsoonal flow from the north brings in vast amounts of moisture from the Caribbean and central Atlantic to fuel scattered thunderstorms across central Brazil.

But this season so far has been different. We have seen extremely strong fronts moving through Argentina and southern Brazil, bringing these areas enhanced rainfall. But these fronts have also been able to clear central and even northern Brazil, leaving cooler, drier air in their wake and leading to very odd conditions that agricultural producers in the region are not used to.

They are used to the daily showers and thunderstorms, especially after mid-October. But the dry spell that they find themselves in now is not one they expect. Instead, these fronts have messed up the monsoonal transport of moisture into the region and have left them awfully dry so far during the month of October.

Some areas are a full 50 millimeters (about 2 inches) short of normal rainfall. Some areas, even more. The couple of periods of rainfall so far this month have been intense when they have happened, but the amount of rain-free days is a bit alarming. When skies clear and temperatures rise, the soil moisture that is around quickly evaporates into the atmosphere and is drying out some areas a bit too much. Producers have been using the extra dry time to quickly plant their soybeans in the region, but the germination of these seeds is in question. They need their regular daily rain, and they need it fast.

In contrast, soil moisture over southern Brazil and Argentina is reportedly very high. The Rosario Grain Exchange is forecasting a significant boost to winter wheat production in Argentina because of it. The first wave of corn planting is reportedly going very quickly as well, according to the Buenos Aires Grain Exchange.

Some meteorological data is unavailable due to the U.S. government shutdown, but reported conditions across southern Brazil are very good as well. The state government of Parana notes that full-season corn planting is nearly finished, and soybean planting is more than half completed. Conditions for both are mostly good to excellent so far, owing to high soil moisture in this week's report.

Another front is moving through Argentina this week and is already producing good rainfall over the country. That front is forecast to move into southern Brazil this weekend and should make its way into central Brazil by the middle of next week. That front may stall out in central Brazil and restart the showers the region desperately needs after bringing through yet another round of good rainfall for Argentina and southern Brazil. We could see another in the early days of November do the same. But long-range models are calling for a change in the weather pattern for most of November.

Both longer-range versions of the American GFS and European ECMWF models are forecasting the month of November to clock in with wetter conditions over central Brazil, but drier and warmer conditions over southern Brazil and Argentina. Fronts and system may start to slow down and their influence on the weather pattern may drop off in November, especially around the middle of the month.

This may start to be the expected pattern due to La Nina building in the Pacific Ocean. Typically, La Nina leaves southern Brazil and Argentina hotter and drier, especially during the summer months of December through February, by offering fewer fronts and systems to move through these areas.

In contrast, the condition can lead to more pronounced rainfall in central Brazil but doesn't have to. At other times, rainfall has a more typical coverage and intensity for the time of year. We can still see periods of dryness developing during La Nina in central Brazil, so this region may not be out of the woods.

Developing crops across the continent are at risk of this being a more typical setup for the summer growing season and could lead to good conditions across the south worsening, while irregular conditions across the north improving.

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John Baranick can be reached at john.baranick@dtn.com

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