La Nina

La Niña (/lɑːˈniːnjə/, Spanish pronunciation: [la ˈniɲa]) is a coupled ocean-atmosphere phenomenon that is the 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. In the United States, an appearance of La Niña persists for at least five months. It has extensive effects on the weather in North America, even affecting the Atlantic Hurricane Season.

La Niña is the positive 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 Nino 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 6 consecutive months or longer.

...
Wikipedia