El Nino is a yearly rhythmic fluctuation of waters from the western Pacific to the eastern Pacific. Some years it is a strong fluctuation and some years it is a weak fluctuation. The reasons for this patterning are obscure and complex. This site offers one way of looking at el nino which seems to accurately describe many phenomena surrounding el nino. The first chart shows the standard divisions of the Pacific which climatologists use to describe the important zones in an el nino.
This chart shows the conditions in December and January in the western Pacific. There is most often a rising of the sea surface temperatures (SSTs) in nino 5 during these months each year.
By February the warm water makes its way eastward into western nino 4.
In March the warm water fills nino 4 and nino 5.
By April of each year the whole western Pacific is usually the site of a warm pool of sea water which is moving eastward into western nino 3.4.
In May of each year cool water emerges in nino 5 and warmth continues to flow eastward.
By June the cool water has flowed into nino 4 and the warm water is approaching the dateline area west of Hawaii in the center of nino 3.4.
In July of each year the warm water hesitates at the dateline as the cool water spreads through nino 4. This is a critical time for the evolution of an el nino. If there is no support for the continued eastward flow of warm water at the dateline then the el nino starts to fade.
By August-September the cool and the warm areas meet and mingle in western nino3.4 . This is the signal that the el nino will usually not evolve further as the warm and the cool neutralize each other.
October, November and December the two masses merge and neutralize in nino 3.4 at the dateline. This signals the end of the yearly el nino event. The neutralization occurs because there are no conditions at the dateline which would support the ongoing eastward migration of warm water from the mid Pacific. In the next series an enhanced el nino event is depicted.
The whole phenomenon.
Read Enhanced/Successful El Nino, next.