Peoria, Ill. (WMBD) — After a rare triple dip La Niña, El Niño is back and is expected to persist well into 2024. So how might this impact our upcoming winter? Let’s go back and take a look at some past El Niño winters and see if we can identify any trends.
What is the El Niño Southern Oscillation (ENSO)?
ENSO consist of three phases, El Niño (positive phase), Neutral, and La Niña (negative phase). Each phase is determined by sea surface temperatures (SST) and how they compare to the long term average along with stronger atmospheric wind pattern over the equatorial Pacific.
El Niño (Positive Phase) – This phase occurs when sea surface temperatures across the central and eastern Pacific are above average. This often results in less rainfall over Indonesia and increased rainfall across the central and eastern Pacific. Shifting winds near the equator will carry tropical moisture north into North America. This typically leads to cooler and wetter seasons across the southern U.S. while warmer and drier seasons occur across the northern U.S. and the Midwest.
What do past El Niño winters look like for Central Illinois?
El Niño is expected to be moderate to strong from December through February. While ENSO isn’t the only teleconnection to impact how things play out over the winter, it may help shape it. We had moderate to strong El Niños during the following winters, 1957-58, 1972-73, 1991-92, and 2009-10 so here’s a look back at what those El Niño winters looked like.
The temperatures during the winter lined up well with what is typically seen during and El Niño winter, warm across the northwest and cooler over the south. Illinois was in a bit of a transition zone and saw temperatures close to average, except for a narrow zone of below average temperatures along the Illinois River Valley.
Precipitation varied across the country but the west and east coasts both had wet winters. Meanwhile parts of the Upper-Midwest were dry along with portions of the south. It was a mixed bag across Illinois with above average precipitation in the south and drier in the north.
With the exception of the northeast and parts of the south, much of the country experienced below average snowfall. This was also the case for much of Illinois, especially south of I-74.
This winter saw below average temperatures across the western U.S. while above average temperatures were generally seen in the east. For Illinois it was a warmer than average winter, especially for the northern half of the state.
Above average precipitation was seen across parts of the south, west and Midwest while drier than normal conditions were experienced over the northern Rockies. For Illinois above average precipitation was experienced west of the Illinois River while below average precipitation was seen further east.
In typical El Niño fashion, parts of the south experienced above average snowfall while much of the Midwest and the Ohio River Valley saw below average snowfall. While the 70s were a rather snowy decade for Central Illinois, that wasn’t the case this winter as much of the state only saw 50-75% of their normal snowfall.
The El Niño blowtorch was cranked to 10 this winter as the plains, Midwest and northern Rockies saw temperatures well above average. This includes Illinois which experienced a winter with temperatures more than 4.5° above average.
Above average precipitation was experienced across the south while below average precipitation was seen across the northern Rockies and the Ohio River Valley, including Central Illinois.
There wasn’t much snow across the country this winter as below average snowfall was experienced from the west coast to the east coast. There were a few pockets of above average snowfall across the south and the upper-Midwest.
When it comes to moderate-strong El Niño winters, this one was a bit of an outlier. Nearly the entire country experienced below average temperatures, including Illinois.
While the northern Rockies and Ohio River Valley saw below average precipitation, the Northern Plains and parts of the Midwest experienced above average precipitation. For Illinois western parts of the state were wetter than normal while areas to the east were drier.
With below average temperatures over much of the country it’s not much of a surprise to see above average snowfall, particularly across the south. Even the Central Plains and the Midwest saw above average snowfall.
After looking at these past El Niño winters there are some recurring themes that have taken shape.
- Below average temperatures were generally experienced across the south and along the east coast while warmer than normal conditions were experienced in the north.
- Above average precipitation was typical throughout the south, the east coast and throughout California. Meanwhile below average precipitation was experienced over the northern Rockies, Great Lakes and the Ohio River Valley.
You can see those trends in the maps below…
For Illinois a couple of points seem to become clear about strong El Niño winters. With the exception of the 2009-10 winter, most El Niño winters tend to favor warmer temperatures and near to below average precipitation. One of the most obvious takeaways from these stats are that strong El Niño winters tend to not be snowy winters in Illinois.
There are other factors that come into play when it comes to how a winter ultimately takes shape, but as an early indicator for a seasonal forecast, it would not be surprising if Central Illinois experiences a warm and not-so snowy winter.
The Climate Prediction Center’s early winter outlook for December, January and February resembles the typical El Niño pattern with above average temperatures over the north, above average precipitation in the south and below average precipitation in the north.