La Niña is a weather pattern that occurs in the Pacific Ocean.
During normal years, winds push warm water from South America to Indonesia. As the water moves, cold water is bring up to the surface from deep in the ocean along South America.
With La Niña (which means little girl in Spanish), the trade winds that affect this action are stronger than usual and more warm water is funneled towards Asia. The subsequent churning of water from the deep ocean makes the waters around the Equator up to 5 degree C colder than normal.
The change in ocean surface temperatures affects rainfall. Precipitation tends to form over warmer ocean waters so areas in Asia like Indonesia and Australia will experience higher than normal rainfall and flooding.
When La Niña occurs, the Pacific jet stream is redirected to a more northerly path, which normally flows across the Pacific Northwest. As a result, this region frequently has wetter-than-average winters; the jet stream also becomes more wave-like, bringing more cold air down into the Pacific Northwest than in non-La Niña years.
The presence of La Niña has a significant impact on US weather and climate which includes increased severe spring weather and tornado activity over the United States’ Southeast.
The ocean surface temperature patterns during La Niña are the opportunity of El Niño (which means little boy in Spanish). During El Niño years, water in the Equator is warmer than normal and wetter conditions tend to shift down the West Coast towards California. More: How El Niño and La Niña Affect Rain in the United States.
How rare is a triple dip La Niña?
Although not on a regular cycle, La Niña events typically occur every few years.
The occurrence of La Niña can commonly occur in two consecutive years. The occurrence of La Niña conditions three years in a rare is rare. Since 1950, a triple dip La Niña has only happened twice.
Current predictions have given La Niña a strong probability of persisting into 2023, making it a triple dip event. The current La Niña started around September 2020.
The World Meteorological Organization issues a press release on June 10, 2022 that stated, “There is a high probability that the ongoing protracted La Niña event, which has affected temperature and precipitation patterns and exacerbated drought and flooding in different parts of the world, will continue until at least August and possibly to the northern hemisphere fall and start of winter.”
On July 5, 2022, NOAA’s Climate Prediction Center released this statement: “Though La Niña is favored to continue through the end of the year, the odds for La Niña decrease into the Northern Hemisphere late summer (52% chance in July-September 2022) before slightly increasing through the Northern Hemisphere fall and early winter 2022 (58-59% chance).”
The prolonged effects of La Niña will likely further exacerbate drought conditions that have hammered much of the western and southwestern United States. In southeast Asia and Australia, flooding will likely to continue to be severe.
References
Becker, E. (2022, May 12). May 2022 ENSO update: Piece of cake. Climate.gov. https://www.climate.gov/news-features/blogs/enso/may-2022-enso-update-piece-cake
ENSO: Recent Evolution, Current Status and Predictions. (2022, July 5). Climate Prediction Center, NOAA. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf
Jones, N. (2022, June 23). Rare ‘triple’ La Niña climate event looks likely — what does the future hold? Nature. https://www.nature.com/articles/d41586-022-01668-1
Stubborn La Nina persists. (2022, June 10). World Meteorological Organization. https://public.wmo.int/en/media/press-release/stubborn-la-niña-persists
What are El Nino and La Nina? (n.d.). NOAA’s National Ocean Service. https://oceanservice.noaa.gov/facts/ninonina.html
