Warm pool - (n.)

In the western equatorial Pacific, this is a region of warm surface waters with a temperature close to 29°C (85°F) and covers an area roughly the size of North America. Normally, the warm pool is fed by Pacific trade winds moving warm tropical surface waters to the west, piling it up in the region between Indonesia, the Philippines, and New Guinea. Warm water gives off heat and moisture to the atmosphere, so the western tropical region becomes a great center for convection and rainfall on the globe. Also, the heat from the warm pool feeds energy to tropical storms there. For reasons yet unknown, during certain years, the trade-winds weaken, and warm surface water is no longer carried westward. On the contrary, the piled-up warm-pool water starts moving east, taking the convection region with it. The surface waters in the eastern region become warm, and now suddenly the tropical storms occur in the region of Tahiti. The coral there suffer from being too warm, and shed their color-giving algal symbionts. In contrast, drought strikes in the western areas, which are no longer in the convection center (e.g. New Guinea and Indonesia). This change in condition produces the "El Niño" effect. See also El Niño