Madden Julian Oscillation ImpactsNOAA / NWS / NCEP Climate Prediction Center Jon Gottschalck and Wayne Higgins 1. What is the Madden-Julian Oscillation (MJO)? The Madden-Julian Oscillation (MJO) is a tropical disturbance that propagates eastward around the global tropics with a cycle on the order of 30-60 days. The MJO has wide ranging impacts on the patterns of tropical and extratropical precipitation, atmospheric circulation, and surface temperature around the global tropics and subtropics. There is evidence that the MJO influences the ENSO cycle. It does not cause El Niño or La Niña, but can contribute to the speed of development and intensity of El Niño and La Niña episodes. 2. How does MJO activity vary over the course of the year? The MJO is often quite variable, with periods of moderate-to-strong activity followed by periods of little or no activity. Because MJO impacts are well known, especially in the global tropics, periods when the MJO is active offer opportunities for enhancing NWS climate prediction and decision assistance. Typically, the northern Hemisphere late fall,
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