Torrential downpours and mud slides besiege southern California while the Northeast United States has fewer hurricanes and a mild winter. Normally the winds blow east to west across the southern Pacific. These winds travel along the surface of the sea and bring warm surface water along with them to the western coasts. As the warm surface water is pushed away from the coasts of Peru, colder, nutrient-rich water rushes up to take its place. In the west, the warm water that's pushed along raises sea levels.
Warm water sloshes back east in a vast, slow wave.
The cooler, rich waters drop along with the thermocline, driving the anchovy population down with it, or killing off a large portion. This in turn reduces the number of marine birds who feed on the anchovy. Courtesy of the Center for Climate Analysis . Since the turn of the century, scientists believed this phenomena occurred independently of any other weather patterns. But in the last few decades, they have learned that pressure changes and wind currents also play a vital role.