A strong El Niño, potentially historically strong, is possible this winter, according to National Weather Service forecasters.
The phase of the El Niño-Southern Oscillation (ENSO) is one of the most important climate phenomena when it comes to forecasting as well as the weather’s outcome in a given location. This is because this has the ability to change the global circulation, which then has an impact on temperatures and precipitation.
An El Niño is when the sea surface temperatures in the central and eastern Pacific Ocean, along the Equator, is at least 0.5°C warmer than the long-term average. The last three winters we have experienced a La Niña, where the temperatures were 0.5°C cooler.
The Climate Prediction Center’s (CPC) forecast is 100% that we will have an El Niño through February. They also have a 73% chance that we will see a strong El Niño. The last time we had a strong (1.5°+) El Niño, was back in the winter of 2015-2016.
Here's what that means for the Tri-State:
When ENSO is in an El Niño phase, that leads to the Pacific Jet Stream shifting to the south of its neutral position, while the Polar Jetstream shifts further to the north. This generally leads to a warmer and drier winter for areas in the Northern U.S. and Canada, while wetter than normal periods and increased flooding is possible for the southern U.S. and the U.S. Gulf Coast.
Here in the Tri-State we are stuck in the warmer and drier general categories. While it would be easy to say that is how our winter will wind up, that to me seems like a cop out. Let's see if we can use past data to see if there are any trends to pick up on.
Before we give a forecast for the winter, we have to define what a “normal winter” is for the Tri-State. While the winter months are defined as December, January and February, we can see snow from October through April. So when it comes to snowfall, the seasonal average for Cincinnati is 23.5 inches over the last 30 years. We will use the winter months to define the average temperature, which equates to 33.9°. These numbers will be our comparison points.
In the last 30 years, we have seen nine El Niño winters, eight neutral winters and 13 La Niña winters. Below is the list of the nine years with El Niño phases and where we finished among snowfall and temperatures in those respective years.
Lets take a look at the climatology those years and see if we can see whether or not there was a trend for El Niño winter outputs here in the Tri-State.
Of those nine El Niño winters, six finished with ABOVE average snowfall, while three finished with BELOW normal snowfall. As for temperatures, five winters finished ABOVE normal while four finished BELOW normal.
There doesn't seem to be too much of a trend to either of those, but the snowfall is the one that has more of a trend. But as mentioned earlier, this El Niño could be one of the strongest on record. Is there a correlation between the strongest El Niño winters and a pattern? Lets look at all winters with a sea surface temperature anomaly of +1.5°+.
This time there was once again more of a correlation with the snowfall results, which finished six below and two above, compared to the temperatures, both four ABOVE and BELOW normal. However, of those last five strong years, four of them did finish with above average temperatures. The winters of 1965-66, 1972-73 and 2009-10 were the only three winters to have a strong El Niño winter immediately following a La Niña winter. Of those three, all of them finished with below normal seasonal temperatures.
With all of that being said, I would still suspect that we see a warmer than normal winter with below normal snowfall.
In my forecast for last year’s winter I said:
“It is still too early to know if we will definitively see a La Niña this winter, but if we do, I would suspect that we see a warmer than normal winter with below normal snowfall.”
Last year finished with an average temperature of 38.6° (above normal) and only 14.4” of snow (well below normal). Let’s see if we can make it two years in a row!
