What is La Nina?

La Niña is an extreme phase of a climate cycle that occurs naturally. The climate cycle involved is a coupled ocean-atmospheric occurrence resulting from the interaction between the atmosphere and the surface of the ocean. Known as the Southern oscillation, this climate cycle includes El Niño on one extreme and La Niña on the other. La Niña is the cold phase of the cycle. A La Niña pattern exists when unusually cool sea-surface temperatures occur in the eastern and central tropical Pacific Ocean around the equator in the area between the International Date Line and the coast of South America.

Taken together, La Niña and El Niño generally are viewed by scientists as among the most powerful of weather phenomena on the planet, because they can affect the climate over more than half the Earth. On average, this cycle of cold surface ocean temperatures occurs every three to five years and, typically, lasts about nine to 12 months. Cold episodes are important because they disrupt the usual patterns of atmospheric circulation and tropical precipitation. The effect of the disruption of these patterns is to enhance the normal climate that prevails in affected regions of the earth.

During a La Niña, for example, an area such as the Pacific Northwest in the United States, where there usually is a wet winter, would have a winter that is wetter than normal. On the other hand, the more arid climates of the southwestern U.S. would be drier than normal, and the rest of the country would tend to experience unusually warm weather during a La Niña cycle. Southeast Asia and India probably would have abnormally heavy monsoonal rains, and eastern Australia could be wetter than usual. This weather effect extends as far north as western Canada, where it causes colder winters, and as far east as southeastern Africa, where the winter weather tends to become cooler and wetter.

La Niña also affects the intensity and position of the jet streams; this, in turn, affects both the track and intensity of storms. During this cold cycle of ocean temperatures, the chances of hurricane activity affecting the Caribbean and the U.S. increase, as does the likelihood that the storms will be more intense. In addition, a strong jet stream is a necessary ingredient for severe weather such as tornadoes. A change in the position of the jet streams affects which regions are most likely to experience tornadoes in the U.S.

La Niña is a climate pattern characterized by cooler-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean. It's part of a larger oscillation known as the El Niño-Southern Oscillation (ENSO) cycle, which also includes the warm phase, El Niño. La Niña events can influence weather patterns across the globe, often leading to increased rainfall in some regions and drought in others.

La Niña events typically occur every 3-5 years but can sometimes happen in consecutive years. According to the National Oceanic and Atmospheric Administration (NOAA), the phenomenon usually lasts between 9-12 months, although some episodes may persist for up to two years. The irregular intervals between events make long-term predictions challenging.

La Niña's impacts are wide-ranging and can lead to significant weather variations across the globe. It's often associated with wetter-than-normal conditions in Southeast Asia, Australia, and South America, while the southern United States and East Africa may experience drier conditions. La Niña can also contribute to a more active Atlantic hurricane season and colder winters in the northern latitudes.

Yes, La Niña can affect global temperatures. While it typically brings cooler ocean temperatures in the equatorial Pacific, its influence on global weather patterns can lead to variations in regional climates. For instance, during La Niña years, some regions may experience lower temperatures, while others could see a rise, depending on prevailing wind patterns and ocean currents.

La Niña is detected and monitored through a combination of satellite observations, ocean buoys, and sea surface temperature measurements. Scientists use these data to analyze changes in the Pacific Ocean's temperature patterns. The Climate Prediction Center (CPC) of NOAA provides regular updates and forecasts on ENSO conditions, helping to predict the onset of La Niña events.

La Niña and El Niño are opposite phases of the ENSO cycle. La Niña represents the cool phase with below-average sea surface temperatures in the tropical Pacific, while El Niño is the warm phase with above-average temperatures. These phases have contrasting effects on global weather patterns, with El Niño often leading to opposite impacts of those associated with La Niña.