A La Nina has developed and will extend through the second winter in a row, according to NOAA’s Climate Prediction Center — a division of NOAA’s National Weather Service. La Nina is a natural ocean-atmospheric phenomenon marked by cooler-than-average sea surface temperatures across the central and eastern Pacific Ocean near the equator and is translated from Spanish as “little girl.”
La Niña intensifies the average atmospheric circulation—surface and high-altitude winds, rainfall, pressure patterns—in the tropical Pacific. Over the contiguous United States, the average location of the jet stream shifts northward. The southern tier of the country is often drier and warmer than average.
A typical La Niña winter in the U.S. brings cold and snow to the Northwest and unusually dry conditions to most of the southern tier of the U.S. The Southeast and Mid-Atlantic also tend to see warmer-than-average temperatures during a La Niña winter.
New England and the Upper Midwest into New York tend to see colder-than-average temperatures.
La Nina is one part of the El Nino Southern Oscillation (ENSO) cycle, which is characterized by opposing warm and cool phases of oceanic and atmospheric conditions in the tropical Pacific Ocean. Consecutive La Ninas following a transition through ENSO neutral conditions are not uncommon and can be referred to as a “double-dip.” In 2020, La Nina developed during the month of August and then dissipated in April 2021 as ENSO-neutral conditions returned.
“Our scientists have been tracking the potential development of a La Nina since this summer, and it was a factor in the above-normal hurricane season forecast, which we have seen unfold,” said Mike Halpert, deputy director of NOAA’s Climate Prediction Center. “La Nina also influences weather across the country during the winter, and it will influence our upcoming temperature and precipitation outlooks.”
This La Nina is expected to last through the early spring 2022. For the upcoming winter season, which extends from December 2021 through February 2022, there is an 87% chance of La Nina.
Previous La Ninas occurred during the winter of 2020-2021 and 2017-2018, and an El Nino developed in 2018-2019. When neither climate pattern is present, ENSO is neutral and does not influence global climate patterns.