Atmosphere Journal Entry

La Niña Will Stay Through Spring (February 16, 2009)

La Niña, the climate pattern known as El Niño's "little sister," will likely stick around through the end of spring, according to a new report from the U.S. Climate Prediction Center. It's expected to gradually weaken from now until the end of April. Then it will fade away and normal ocean temperatures will return to the Pacific Ocean. La Niña is marked by cooler ocean temperatures in the central and eastern Pacific Ocean along the equator. It's the opposite of El Niño, which brings warmer ocean temperatures to the equatorial Pacific.

Like it's more famous "brother," La Niña affects weather around the globe but usually in a milder way. Some of its weather effects are the opposite of those brought by El Niño. For the United States, it could mean wetter than normal weather in the Ohio and Tennessee valleys and drier weather across the Southeast and Southwest over the next few months. It might also bring colder weather to the Northwest and warmer weather across the southern United States.

La Niña changes the flow of the jet stream, the weather "superhighway" high in the atmosphere over North America. This tends to increase Atlantic hurricane activity by reducing wind shear that tears storms apart. That won't be a problem this year if La Niña weakens as expected.