As winter rapidly approaches, it’s time to look at current conditions and weather patterns expected to impact North America during the next six months.
Although the temperature and precipitation patterns in October 2016 were similar to those in October 2015, the underlying causes were polar opposite patterns in the Equatorial Pacific. Last year we were entering an exceptionally strong El Nino in October, while this year a weak to moderate La Nina appears to be unfolding.
We know that weather patterns around the globe are influenced by conditions in the Equatorial Pacific and that these patterns are usually dominant during the North American winter. The impact of stronger events can last into the late spring or span multiple years. Impacts to agricultural production are greatest for the Southern Hemisphere where La Nina and El Nino events impact yields with correlations of 70% or greater.
La Nina conditions are generally a net positive for Southern Hemispheric agricultural production. The general tendency is for Australia to experience above normal wheat yields and for southern Brazil to trend toward above normal soybean yields. South Africa has a positive corn yield correlation, while Argentina corn yields are more drought prone. Under El Nino conditions, polar opposite yield trends are most common for these four countries.
In the US the dominant winter trend during a La Nina event is for wet conditions across the Pacific Northwest southward through northern California, along with the eastern Corn Belt. Drier than normal conditions materialize across the southern third of the United States. During El Nino years, these same areas exhibit opposite trends.