An El Niño occurs when abnormal sea surface temperatures and air pressure patterns in the tropical Pacific Ocean reinforce each other to produce a sustained period with above-average temperatures in the central to eastern equatorial Pacific Ocean and weaker or reversed trade winds. At the same time, the weaker winds and heat beneath the surface of the sea block the upward movement of cooler, nutrient-rich ocean waters. El Niño events typically last nine to twelve months, or as long as sea surface and subsurface temperatures stay warm enough to sustain these ocean-atmosphere interactions, resulting in abnormal weather patterns.
Signs of El Niño events are routinely monitored and predicted using observations and climate models. The ability to predict El Niño events improves after the northern hemisphere spring. El Niño events can begin as early as summer and typically reach peak strength during fall or winter in the northern hemisphere.
Although the amount of precipitation can vary from one El Niño to the next, consistent patterns across past events provide a baseline for predicting future impacts in remote areas. These assumptions are based on historical El Niño impacts, the expected strength and duration of related weather events, and other regional factors.
El Niño Triggers Food Crisis in Southern Africa
El Niño events alter global atmospheric circulation, making certain regions around the world more likely to experience above-normal or below-normal seasonal precipitation or temperatures. An El Niño occurs when abnormal sea surface temperatures and air pressure patterns in the tropical Pacific Ocean reinforce each other to produce a sustained period with above-average temperatures in the central to eastern equatorial Pacific Ocean and weaker or reversed trade winds. At the same time, the weaker winds and heat beneath the surface of the sea block the upward movement of cooler, nutrient-rich ocean waters. El Niño events typically last nine to twelve months, or as long as sea surface and subsurface temperatures stay warm enough to sustain these ocean-atmosphere interactions, resulting in abnormal weather patterns.
Signs of El Niño events are routinely monitored and predicted using observations and climate models. The ability to predict El Niño events improves after the northern hemisphere spring. El Niño events can begin as early as summer and typically reach peak strength during fall or winter in the northern hemisphere.
Although the amount of precipitation can vary from one El Niño to the next, consistent patterns across past events provide a baseline for predicting future impacts in remote areas. FEWS NET’s agroclimatic assumptions help to inform projections of future food security outcomes in the countries we monitor. These assumptions are based on historical El Niño impacts, the expected strength and duration of related weather events, and other regional factors.
