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El Niño–Southern Oscillation (ENSO)

The el niño–southern oscillation (enso) is a phenomenon that occurs in the tropical Pacific Ocean approximately every two to five years and typically lasts nine to 12 months. ENSOs, and the opposite condition, called La Niña, represent severe disruptions of the normal weather patterns over the Pacific and have significant impacts on weather around the world. These events typically start around August, reach their peak intensity in December through April, and dissipate in the spring and early summer. However, particularly strong events can persist for up to four years.

Anatomy of the Phenomenon

Under normal conditions, the northeast trade winds push surface waters westward across the tropical Pacific ocean. These waters warm as they absorb solar energy and pile up in the western Pacific near Australia and ...

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