The Curious Case of the El Niņo That Never Happened: A perspective from 40 years of progress in climate research and forecasting

Forty years ago, Klaus Wyrtki of the University of Hawaii launched an "El Niņo Watch" expedition to the eastern equatorial Pacific to document oceanographic changes that were expected to develop during the onset of an El Niņo event. He and his colleagues used a very simple atmospheric pressure index to predict the event and convinced the National Science Foundation and Office of Naval Research to support an expedition to the eastern Pacific on relatively short notice. Initial warming was detected during the expedition, which took place in early 1975, but it quickly dissipated and El Niņo did not develop. The results of the expedition were published in Science in 1976. Wyrtki and colleagues offered no explanation for the failed forecast or for why the initial warming did not amplify. Nor did they present a basin scale perspective of what was happening prior to and during the expedition for lack of data. The expected "1975 El Niņo" did not occur, which underscored our fundamental ignorance about this major climate phenomenon. As such, it served as a stimulus to further research that helped lay the foundation for TOGA in the 1980s and 1990s. This paper addresses why the forecast failed, provides a broad scale context for what the expedition observed, and elucidates the dynamical processes that gave rise to the abbreviated warming that was detected. We will also present retrospective forecasts of the event using coupled ocean atmosphere dynamical model prediction systems.