Abstract:In early 2015, the tropical Pacific Ocean appears to be primed for a potentially significant El Niño event, and some similarities exist between the oceanic and atmospheric states compared to the observations shortly before the onset of the 1997 Super El Niño event. Associated with the enhanced westerly winds and the eastbound migration of the warm water over the equatorial Pacific, subsurface warm water tended to accumulate over the eastern equatorial Pacific, and the warming of ocean temperature in the eastern basin was getting more obvious. After October 2015, the sea surface temperature over the eastern equatorial Pacific was 2.0-3.0℃ warmer than the normal condition, developing to the strongest El Niño event in 21^st century. Different from the status that most El Niño model from operational centers over the world didnot predict the event 6-9 months ahead, the developed El Niño forecasting system(i.e., the ensemble prediction version developed in the Institute of Atmospheric Physics), was supported by the"Western Pacific Ocean System:Structure, Dynamics and Consequences"Project of the Chinese Academy of Sciences(CAS), successfully predicted the onset, development, and amplitude of this El Niño event 9 months in advance. This successful forecasting result further significantly supported the climate prediction and the disaster prevention and mitigation in China. At the same time, the other version of the El Niño forecasting system(i.e., a deterministic system developed in the Institute of Oceanology, CAS), for the first time, started to release the realistic El Niño forecasting result at the website of the University of Columbia in US.