A large pool of warm water is located in the central and western part of the Pacific Ocean. Atmospheric conditions can increase the temperature of the surface water. As a result, this pool of warm water enlarges and shifts eastward to cover the tropics. El Nino also causes a decrease in the eastward flow of the trade winds. On the eastern side of the Pacific, parts of Australia, New Zealand, the Philippines and Indonesia experience drought conditions. The effect can spread as far as India. The opposite happens in North and South America where the general climatic conditions are wetter and warmer temperatures.