Last year, weather forecasters spent a lot of time talking about something called an “El Niño,” a weather phenomenon that affects weather on a global scale. This year there has been slightly less buzz about “La Niña,” El Niño’s opposite. But what is La Niña, and what does it mean for our weather?
La Niña is part of a larger weather phenomenon known as El Niño Southern Oscillation, a fluctuation in the surface sea temperatures in the Pacific Ocean. While El Niño events feature unusually warm sea temperatures near the Equator, a La Niña is characterized by unusually cold water temperatures in the same region. La Niñas generally occur rather erratically, about once every three to five years, and typically last between 9 and 12 months. They often, but not always, follow on the tails of an El Niño.
In Spanish, “la niña” means “the little girl.” It got its name as a direct response to the phrase “El Niño,” which means “the little boy,” the Spanish diminutive often used to denote the Christ Child. El Niño was originally named in the 19th century, when Peruvian sailors noticed that every few years, around Christmastime, coastal waters warmed, and the Pacific Ocean current shifted southward. La Niña was eventually adopted to describe the opposite effect.
What causes a La Niña?
Scientists are still trying to determine what causes Southern Oscillation. The abnormally warm ocean temperatures associated with an El Niño event often result in the subsequent cooling of a La Niña event, but the underlying cause of both conditions is still a mystery. During the last century, La Niñas have occurred in 1916, 1924, 1928, 1938, 1950, 1954, 1964, 1970, 1973, 1975, 1988, 1995, 1998, 2000, 2007, and 2010, usually beginning in the fall and continuing into the following spring. Since 1975, La Niñas have been about half as frequent as El Niños.
How does La Niña affect the weather?
La Niña has the opposite affect on global weather as its brother. Whereas El Niño wreaks havoc on weather, often making wet places dry, and vice verse, La Niña basically magnifies the usual weather conditions. In the northeastern United States, where cold and snowy winters are the norm, La Niña causes even more cold and snow to descend, making for extremely brutal winters. In the Pacific Northwest, La Niña causes things to be even wetter than usual, while arid Southwestern states often see drier than normal conditions. Things get really dangerous during the spring and summer of a La Niña, because tornado and hurricane seasons are often longer and more dangerous.
How long can a La Niña last?
The longest recorded La Niña lasted from the spring of 1973 through the spring of 1976, a period marked by drought conditions throughout much of the United States, while other parts of the world saw devastating flooding, with storms that claimed hundreds of thousands of lives. Don’t let the name fool you, La Niña is no sweet little girl!