ASK THE METEOROLOGIST
“Why does El Nino make storms?”
Lillyann
El Nino impacts the weather not just here in the United States but across the entire globe. The El Nino Southern Oscillation is an oceanic phenomena that refers to a warm pool of water typically located just north and east of Australia.
During an El Nino, this warm pool of sea surface temperatures shift east ..into the Central Pacific. This tends to happen every 3-7 years and it is still unknown exactly why this happens. It is known though, that when this shift happens ..the southeast trade winds just south of the equator weaken. This is partially why this warm pool is able to move eastward.
The sea surface temperatures rise between 3 and 10 degrees ..bringing ocean temperatures into the 80’s in some locations! This in turn warms the area close to the ocean. That warm air is picked up by the northeast trade winds, north of the equator and deposited across the entire globe through the other prevailing winds.
This influences temperature and precipitation patterns across all continents. Here in the U.S. we tend to see a “split flow.” Meaning, the jet stream is essentially broken in two. There is a jet stream (or storm track) that tends to stay over Canada and dip across the Great Lakes states and there is also a Pacific jet stream that brings storms to the southern tier of our country. Both of these jets lead to temperature and precipitation trends across the continental U.S.