South America Calling

Subpar Rain in Brazil Forecast

Bryce Anderson
By  Bryce Anderson , DTN Senior Ag Meteorologist
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The European forecast model shows rainfall totals in the Brazil likely to run 1 to 2 inches below normal through Nov. 20. (DTN graphic)

Dryness is a dominant theme of the Brazil crop season so far. We have already seen the impact of dry conditions in the late start to soybean planting. The first week of brought a return to dry conditions following late-October rain in the top crop areas of Brazil, as USDA's Weekly Weather and Crop Bulletin noted.

"Dry weather returned to most major farming areas stretching from central Mato Grosso southward through Rio Grande do Sul, where moisture has been limited for summer crop development for much of the early season. Given the sporadic nature of rainfall thus far in the season, a return to normal rainfall is vital for sustaining the current yield expectations," stated the Nov. 10 bulletin.

The next seven days do bring showers and thunderstorms across all but southern and far northeastern Brazil. Forecast maps indicate widespread rainfall of 1 to 3 inches in Mato Grosso, Goias, Sao Paulo and Parana. Up to 4 inches of rain may develop in Mato Grosso do Sul and Minas Gerais. Less than a half inch of rain is expected in the northeast state of Bahia and in Rio Grande do Sul in the far south.

Rainfall of 1 to 3 inches sounds like beneficial rain at first hearing. However, keep in mind that we're talking about many locations in subtropical latitudes, where the rainy season is just that -- wet. And, over the period ending Nov. 20, almost all Brazil production areas will have a rainfall deficit of 1 to 2 inches below average. In addition, temperatures are forecast to range from 5 to 10 degrees Fahrenheit above normal across central Brazil; this heat means drying out of rain that occurs and limits the crop moisture benefit.

Ahead of this shower occurrence, crop vegetation is in worse shape than average. Vegetation health index charts show that from Mato Grosso to Rio Grande do Sul, conditions are much worse than normal. Some of that lag is likely due to the result of later planting; but, again, that is a dryness effect.

This rainfall deficit has a strong chance of continuing or increasing as we move toward the heart of the Southern Hemisphere crop season due to the influence of the Pacific Ocean La Nina event.

La Nina is projected to reach its maximum intensity in the December-to-February time frame, right at the reproductive and filling phases of the Brazil soybean crop. The dryness-affected start of soybean planting has also led to a compression of the planting phase, meaning that larger portions of the soybean crop will be going through the flowering, pod setting and pod filling stages at the same time. This is ominous for crop prospects also, since the vulnerability to crop stress will not be as spread out over a longer period of time due to the late planting start.

Going into the last half of the Southern Hemisphere equivalent to the month of May in the Northern Hemisphere, there is a good reason to be watchful of the dry signals in the Brazil weather pattern.


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