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The El Niño of 2015-16 tied the one in 1997-98 as the strongest on record, with Central and East-Central Equatorial Pacific Ocean temperatures peaking at 2.3°C above seasonal norms (Figure 1). Since reaching their peak in December 2015, temperatures have begun to slide. In May, they averaged just 0.7°C above normal, and by July large patches of cooler-than-normal water had cropped up along the Equator on the Americas-facing side of the Pacific (Figure 2). This begs the question: Is the latest El Niño about to develop into a powerful La Niña? La Niña is associated with cooler, wetter conditions along the U.S.-Canadian border and warmer, drier conditions in much of the southern United States, and impacts weather patterns worldwide. Past La Niñas have roiled agricultural markets, sending crop prices on wild rides, with prices often moving lower amid exceptionally high levels of volatility.
The risk of a La Niña is significant. If one looks at the past three El Niños that peaked at 2°C or more above normal, they all transformed into La Niñas within two years, and in one case (1972-73), in as little as six months.