The El Nino Cycle Indeed El Nino, and the role it plays in periodic droughts which hit the Indian subcontinent, was one of the foundational questions that drove modern weather research. In his book on Victorian famines, writer Mike Davis calls the El Nino Southern Oscillation (or ENSO to give it its full name) the "elusive great white whale of tropical meteorology for almost a century". And despite more than a century of research, it still, in a sense, remains that way. El Nino arises in the eastern Pacific, along the coast of South America. In 'normal' years, there exists both a temperature and air pressure difference between the oceans there, and the western Pacific, thousands of miles on the other side, near Indonesia and Southeast Asia. The waters of the eastern Pacific near South America are colder, and are associated with higher atmospheric air pressure over them, as compared with the waters of the western Pacific which are warmer, and are associated with lower atmospheric pressure. As we learnt in high school geography, wind always blows from a region of high pressure to a region of low pressure, and this is what happens over the Pacific, with winds blowing from the east to the west. In turn, the air over the western pacific rises into the atmosphere and then cycles back east, and the whole process starts again. http://articles.economictimes.indiatimes.com/2014-06-22/news/50772456_1_indian-monsoon-eastern-pacific-high-pressure