Note:The ENSO (El Niño Southern Oscillation) Index represents a centered three-month mean SST (sea surface temperature) anomaly for the Niño 3.4 region (i.e.,5oN-5 oS, 120o -170oW). According to the NOAA, events are defined as five consecutive overlapping three-month periods at or above the +0.5 anomaly for El Niño events and at or below the -0.5 anomaly for La Niña events.