The same sort of thing happens in the atmosphere - if you have a hot spot in the water of the tropics, it can cause an outwardly expanding, standing wave pattern. By examining the patterns of past El Ninos and projecting them into the future, scientists can get a pretty good idea of what kind of weather to expect in upcoming months. For example, during an El Nino year, the warm water flowing towards the Americas adds heat and moisture to the air above it. Consequently, the West Coast of South America gets more rain than usual. The southwest Pacific experiences drier than normal conditions.
Hurricanes are stronger in the eastern Pacific and weaker in the Atlantic.
And the effects of El Nino don't stop there. Over Western Canada, for example, the jet stream tends to intensify and run down through California. This leaves a high-pressure area over Western Canada, creating warmer and drier weather, while giving the western U.S. the more humid air. El Nino's cousin, La Nina, also affects worldwide weather. The opposite of El Nino, La Nina causes abnormally cold water to flow across the Pacific Ocean.