It seems like every year that winter weather brings us more snowfall than average, there is talk of an El Nino. But what exactly is an El Nino? And what about the lesser-known La Nina? What should we know about that? In this post, we are going to look at the weather patterns known as El Nino and La Nina to see the impact they can have on winter conditions in the U.S.
The ENSO Cycle
The governing weather pattern in which El Nino and La Nina play opposing roles is the El Nino-Southern Oscillation (ENSO) cycle. The ENSO cycle is the metrological term for the regular fluctuations that occur between the atmosphere and the ocean along the central Equatorial Pacific, which is located between 120 degrees West and the International Date Line.
El Nino is referred to as the warm phase of the ENSO cycle, while La Nina is known as the cold phase of the cycle. The changes from normal surface temperatures in the region have significant effects on the ocean processes, which you would expect. They can also have a tremendous influence on global climate and weather patterns, which is why we are sometimes talking about them in the dead of a Michigan winter.
The ENSO cycle is somewhat predictable in that the alternating episodes usually last about nine to 12 months. On occasion, though, some phases can actually last for years! The frequency of these occurrences can be notoriously irregular, with an ENSO cycle happening every two-to-seven years on average. (How's that for a range?) In general, El Nino happens more often than La Nina.
Breaking Down El Nino
The literal translation of El Nino is "The Little Boy" or even "The Christ Child." Seems innocent enough. The name was chosen by fisherman in the 1600s who first noticed there was unusually warm water off the Pacific coast of South America around December.
Today, the term El Nino is the label for large-scale climate interactions between the ocean and the atmosphere that are defined by episodic warming of sea surface temps along the Central and East-Central Pacific.
The usual effects of El Nino typically start to develop over North America right before winter. These effects include drier-than-average conditions in the Pacific Northwest, Ohio Valley, and the Lower Great Lakes Region. By contrast Florida and the U.S. Gulf Coast region will usually see wetter-than-average conditions. Finally, it leads to warmer-than-average conditions across the western and northern U.S., as well as western and central Canada.
Breaking Down La Nina
La Nina means, as you might expect, "The Little Girl" in Spanish. It behaves in the opposite way El Nino behaves, characterized by lower-than-average sea surface temps along the East-Central Equatoral Pacific. It should come as no surprise, then, that the global climate effects of La Nina tend to be the exact opposite of El Nino. During a La Nina season, winter temps are cooler-than-normal in the Northwest, while the Southwest sees warmer-than-normal temps.
Combined with the often-unpredictable nature the Great Lakes play in winter weather patterns, it should be no surprise that weather conditions starting halfway around the world can set off storms in the Great Lakes area. Understanding just how El Nino and La Nina behave, though, can sometimes help forecast longer-term winter weather patterns.
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