El Niño and La Niña

Have you ever stirred chocolate syrup into a glass of milk and watched the light and dark colors swirl around? Then you already have some understanding of El Niño and his cool sister, La Niña.

El Niño and La Niña are warm and cool masses of water in the Pacific that routinely shift back and forth like milk and chocolate syrup in a glass.

When eastward trade winds weaken, warm water flows into the tropical Pacific. This has typically happened every few years around Christmastime. Fishermen in Peru named this warming of the waters El Niño, after the Christ child. The warm water evaporates into the air more readily than cool water, producing storm clouds. The result is an unusual amount of precipitation all along the coast of the Americas, and reverberations all over the globe, including the central European flood of 1998, cyclones in Madagascar, mudslides in California, and tornadoes in Florida.

La Niña begins with the opposite: A cooling. This year, the eastward trade winds are growing stronger and pushing the warm water out of the tropical Pacific. Cool water is swelling up and surfacing along the coast of the Americas. This translates into La Niña. In places like Peru, La Niña means less precipitation. But the effects around the globe differ. We've seen the effects of La Niña in the record snows in Buffalo and Chicago, the all-time low temperatures in Maine and Indiana, and in the tornadoes in the Midwest.

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