Describe the changes in air pressure that occur during an El Nino year. How do these changes affect wind patters?
During a year with the El Nino effect, there is warming of the surface waters in the eastern Pacific Ocean and the pressure is high in the western Pacific. The opposite is true in years when the cooler La Nina is in effect: cooler water and lower air pressures. During an El Nino, trade winds (which normally go from the southeast toward the west in the southern hemisphere) weaken considerably or even blow toward the east. The resulting changes in wind patterns across the Pacific lead to unexpected weather changes in other parts of the world.