La Nina Climate Pattern Could Bring Snow, Storms to North America

U.S. weather officials announced Thursday that a La Nina climate pattern has developed in the Pacific Ocean, possibly exacerbating an already busy hurricane season and setting up a colder, wetter winter for North America.U.S. Climate Prediction Center Deputy Director Mike Halpert said in a press release that La Nina can contribute to an increase in Atlantic hurricane activity by weakening winds over the Caribbean Sea and tropical Atlantic Basin. He said that can enable storms to develop and intensify.Halpert said the potential for La Nina development was considered when the National Oceanic and Atmospheric Administration (NOAA) updated its Atlantic hurricane season outlook last month.In a statement on its website, NOAA describes La Nina — translated from Spanish as “little girl” — as a natural ocean-atmospheric phenomenon marked by cooler-than-average sea surface temperatures across the central and eastern Pacific Ocean near the equator.In the winter, La Nina typically brings above-average precipitation and colder-than-average temperatures along the northern tier of the U.S., along with below-average precipitation and above-average temperatures across the South. NOAA says that raises concern for the U.S. Southwest, which saw a weak summer rainy season and is already experiencing a severe drought.The opposite effect, El Nino — “little boy” in Spanish — is characterized by unusually warm ocean temperatures in the equatorial Pacific. That can often result in increased rainfall across the southern tier of the U.S., which, in the worst case, can cause destructive flooding, and drought in the western Pacific.NOAA says the most recent La Nina appeared during the winter of 2017-18, and El Nino followed in 2018-19. When neither climate pattern is present, as was the case last winter, the El Nino Southern Oscillation is neutral and does not influence global climate patterns.
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