The El Nino/Southern Oscillation occurs in between the three phases Neutral, La Nina or El Nino.
The humboldt current takes cold water to South America's west coast to the tropics from the Southern Ocean. Because of the welling which takes place in Peru this process is enhanced. Due to the trade winds near the equator the cold water travels west where it heats up due to the sun. This makes the water of the western Pacific warmer.
