La Niña

La Niña (/lɑːˈniːnjə/, Spanish pronunciation: ) is a coupled ocean-atmosphere phenomenon that is the colder counterpart of El Niño, as part of the broader El Niño–Southern Oscillation climate pattern. The name La Niña originates from Spanish, meaning 'the little girl', analogous to El Niño meaning 'the little boy'. It has also in the past been called anti-El Niño, and El Viejo (meaning 'the old man'). During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3 to 5°C (5.4 to 9°F). An appearance of La Niña persists for at least five months. It has extensive effects on the weather across the globe, particularly in North America, even affecting the Atlantic and Pacific hurricane seasons.A timeline of all La Niña episodes between 1900 and 2019. La Niña (/lɑːˈniːnjə/, Spanish pronunciation: ) is a coupled ocean-atmosphere phenomenon that is the colder counterpart of El Niño, as part of the broader El Niño–Southern Oscillation climate pattern. The name La Niña originates from Spanish, meaning 'the little girl', analogous to El Niño meaning 'the little boy'. It has also in the past been called anti-El Niño, and El Viejo (meaning 'the old man'). During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3 to 5°C (5.4 to 9°F). An appearance of La Niña persists for at least five months. It has extensive effects on the weather across the globe, particularly in North America, even affecting the Atlantic and Pacific hurricane seasons. La Niña is the positive and cold phase of the El Niño–Southern Oscillation, and is associated with cooler-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean. However, each country and island nation has a different threshold for what constitutes a La Niña event, which is tailored to their specific interests. For example, the Australian Bureau of Meteorology looks at the trade winds, SOI, weather models and sea surface temperatures in the Niño 3 and 3.4 regions before declaring that a La Niña event has started. However, the Japan Meteorological Agency declares that a La Niña event has started when the average five-month sea surface temperature deviation for the NINO.3 region is more than 0.5 °C (0.90 °F) cooler for six consecutive months or longer. There was a relatively strong La Niña episode during 1988–1989. La Niña also formed in late 1983, in 1995, and a protracted La Niña event that lasted from mid-1998 through early 2001. This was followed by a neutral period between 2001 and 2002. The La Niña which developed in mid-2007, and lasted until almost 2009, was a moderate one. The strength of La Niña made the 2008 Atlantic hurricane season one of the five most active since 1944; sixteen named storms had winds of at least 39 miles per hour (63 km/h), eight of which became 74-mile-per-hour (119 km/h) or greater hurricanes. A new La Niña episode developed quite quickly in the eastern and central tropical Pacific in mid-2010, and lasted until early 2011. It intensified again in mid-2011 and lasted until early 2012. This La Niña, combined with record-high ocean temperatures in the north-eastern Indian Ocean, was a large factor in the 2010–2011 Queensland floods, and the quartet of recent heavy snowstorms in North America starting with the December 2010 North American blizzard. The same La Niña event was also a likely cause of a series of tornadoes of above-average severity that struck the Midwestern and Southern United States in the spring of 2011, and drought conditions in the South Central states including Texas, Oklahoma and Arkansas. Meanwhile, a series of major storms caused extensive flooding in California in December 2010, with seven consecutive days of non-stop rainfall, leading to one of the wettest Decembers in over 120 years of records. This is in contrast to the drier-than-normal conditions typically associated with La Niña in California, especially in the south. In 2011, on a global scale, La Niña events helped keep the average global temperature below recent trends. As a result, 2011 tied with 1997 for the eleventh-warmest year on record. It was the second-coolest year of the 21st century to date, and tied with the second-warmest year of the 20th century. A relatively strong phase of La Niña opened the year, dissipated in the spring before re-emerging in October and lasted through the end of the year. When compared to previous La Niña years, the 2011 global surface temperature was the warmest observed. The 2011 globally-averaged precipitation over land was the second-wettest year on record, behind 2010. Precipitation varied greatly across the globe. This La Niña contributed to severe drought in East Africa and to Australia's third-wettest year in its 112-year period of records. La Niñas occurred in 1904, 1908, 1910, 1916, 1924, 1928, 1938, 1949–51, 1954–56, 1964, 1970–72, 1973–76, 1983–85, 1988–89, 1995–96, 1998–2001, 2007–08, 2008–09, 2010–12, 2016–17, and 2017–18. La Niña impacts the global climate and disrupts normal weather patterns, which as a result can lead to intense storms in some places and droughts in others. Observations of La Niña events since 1950, show that impacts associated with La Niña events depend on what season it is. However, while certain events and impacts are expected to occur during events, it is not certain or guaranteed that they will occur. La Niña results in wetter-than-normal conditions in Southern Africa from December to February, and drier-than-normal conditions over equatorial East Africa over the same period.