KANSAS CITY, MISSOURI, US — Drought in Argentina is quite serious with crop health in early December rated the poorest in nearly 40 years. Significant relief is not likely to evolve during December, although the latter days of this month should offer a little boost in shower and thunderstorm activity. In the meantime, neighboring areas of southern Brazil should dry down and concern over US hard red winter wheat production areas will continue this month. Changes, though, are expected in January and February.

The US National Oceanic and Atmospheric Administration (NOAA) created a Vegetative Health Index (VHI) years ago that is designed to assess vegetative health from infrared satellite imagery. The index views vegetation color from outer space and compares that color to the color of crops in an average year. These satellite estimates of crop condition have become more sophisticated in recent years and the VHI has become an important tool for analysts and agronomists to assess the overall health of crops around the world. The latest imagery and indices reflecting crop conditions in South America have been quite revealing.

Most producers, traders and analysts are fully aware of the lack of rain in Argentina this year. The drought has worsened from that of recent past years when rainfall also was suppressed. The root of Argentina’s limited rainfall has been associated with the presence of La Niña, which tends to reduce moisture in the atmosphere from the middle latitudes of both the Northern and Southern Hemispheres. Spring 2022 in the Southern Hemisphere is the third growing season in a row in which La Niña has dominated the atmosphere and three years of restricted precipitation has presented notable moisture deficits.

Argentina’s rainfall since the start of this growing season has been well below average in many areas, especially in the north and eastern parts of the nation. The prolonged period of restricted rainfall has limited crop moisture at times, and that has seriously stressed crops. The most recent VHI for South America has shown Argentina crops to be seriously stressed by dryness. World Weather, Inc. spent some time looking at historical VHI imagery for Argentina, and after viewing all 39 years of data for early December it has determined that this year’s drought has had the most profound impact on crop health seen in all 39 of those years.

There have been a few years of notable drought in the recent past, but this one seems to be a little more unique in the sense that crops and farmers in Argentina have been fighting dryness since the winter wheat crop was planted late last autumn. Wheat production was slashed this year and what is left of that crop is being harvested, but the yield and quality are seriously lacking because of drought.

Planting of spring and summer crops in Argentina began early in the fourth quarter of this calendar year and many crops have struggled with dryness since that time. Emergence and establishment has not been good, and it has been dry enough multiple times to restrict planting, emergence and establishment. With summer crop planting well behind normal and La Niña prevailing, the obvious question is when will this end?

Scientists have observed changes in the subsurface ocean water of the eastern equatorial Pacific Ocean that strongly hints La Niña’s peak intensity finally has passed. A warming trend deep in the ocean water is expected to shift more to the east and expand in the next few weeks. La Niña conditions are based on surface ocean temperature anomalies in the eastern equatorial Pacific Ocean, and when they are broadly colder than usual, as they have been since 2020, world weather patterns change. The warming of subsurface ocean water is extremely important because of an upwelling current in the eastern equatorial Pacific Ocean that brings subsurface ocean water to the surface.

The upwelling current in the eastern Pacific Ocean will soon be transporting the warming subsurface ocean water toward the surface. As that process evolves La Niña will begin to weaken and diminish. NOAA forecast models have suggested an accelerated weakening trend will occur in La Niña late this month and especially in January and February. The quick diminishing trend in La Niña will open the door of opportunity for changes in world weather patterns. That will translate into a much improved opportunity for rain in Argentina, Uruguay and far southern Brazil, all of which have seen less-than-usual rainfall in recent weeks.

The improving rain potentials in southern parts of South America will help to take down the crop stress, but early season crops already will have suffered great losses in production potential in Argentina, where drought is most serious. Southern Brazil and Uruguay crop stress has not been nearly as significant as that in Argentina, and weather changes in January could maintain a very good production outlook. Argentina’s early season crops, however, are being permanently hurt by dryness. Its late season corn, soybean, sorghum and peanut crops still have huge potentials for improvement if some timely rain can occur in the next few weeks to support planting and keep crops viable until the better days of summer rainfall evolve in January and February.

The same relief from drought that is expected in South America also will occur in North America. Portions of the central United States have dealt with a multi-year drought, too, and relief is needed. US hard red winter wheat production in 2022 was low, and the emergence and establishment of the 2023 crop has not been good with many analysts predicting a very poor crop.

The good news is that La Niña’s weakening trend likely will support improved soil moisture in the first quarter of 2023, and that should give the poorly established wheat crop an opportunity for new root and tiller development in the late winter and early spring. Drought damaged wheat that survives the winter can and will set new tillers and develop better root systems if soil moisture is present when temperatures warm in the early spring.

There have been many La Niña years in which hard red winter wheat in the Plains looked like a failure in the autumn turned around in the spring as La Niña diminished and rain began falling. World Weather, Inc. believes the same trend will occur in 2023.