NiñaPhasen

NiñaPhasen refer to the La Niña phase within the El Niño–Southern Oscillation (ENSO) cycle. They are characterized by cooler-than-average sea surface temperatures in the central and eastern tropical Pacific, especially in the Niño 3.4 region, and by stronger-than-average trade winds that enhance upwelling along the western coast of South America. These conditions disrupt the usual west-to-east transport of heat in the tropical Pacific and produce characteristic atmospheric patterns.

Monitoring and classification rely largely on the Oceanic Niño Index (ONI), a 3‑month running average of SST anomalies in the Niño 3.4 region. La Niña is declared when ONI is at or below -0.5°C for five consecutive 3‑month periods. Intensity is commonly categorized as weak (-0.5 to -0.9°C), moderate (-1.0 to -1.4°C), or strong (≤ -1.5°C).

Impacts of NiñaPhasen vary by region but typically include changes in precipitation and temperature linked to teleconnections. In North America, La Niña often brings cooler, wetter winter conditions to the Pacific Northwest and drier conditions to the southern United States. In parts of the tropics and subtropics, La Niña can enhance rainfall in portions of Southeast Asia and northern Australia, while reducing rainfall elsewhere, such as the central and eastern Amazon basin. The Atlantic hurricane season may see increased activity during La Niña due to reduced vertical wind shear.

NiñaPhasen are part of a natural climate cycle tracked by meteorological organizations worldwide, including the NOAA Climate Prediction Center and the WMO, and are subject to interannual variability and longer-term climate influences.