Source: USA TODAY research by Jack Williams, Graphic by John Herne
Weather disruptions begin in the Pacific
By Jack Williams, USATODAY.com
El Niño refers to a combined ocean-atmosphere pattern, during which the Pacific Ocean's warmest water has shifted from the western Pacific to the central Pacific and the coasts of South American and even North America. (Related: How El Niño begins)
No matter where it is, warm, ocean water supplies both moisture and energy for huge thunderstorms. These thunderstorms, in turn, feed both moisture and wind energy into the upper atmosphere, where they influence the west-to-east winds high above the Earth, known as jet streams. (Related: Jet streams)
When the warm water and thunderstorms move eastward, they help change the jet stream because the are feeding moisture and energy into the upper atmosphere at different places. You can think of the upper air winds as being like a white-water river and the effects of an El Niño as being somewhat like moving some of the rocks in a white-water stream.
Since the upper air winds, the jet streams, help move storms and also help determine where and when storms will begin and end and how strong they'll be, the weather far away will feel the effects of jet stream changes, and thus the effects of an El Niño.
A strong El Niño has very noticeable effects on the USA's weather, which can range from a stormy winter along the West Coast, a wet winter across the South, and a warmer-than average winter for parts of the North. (Related: How El Niño changes USA storm patterns)