Here’s what that means for our weather
A strong El Niño, which is likely to be historically strong, is likely this winter, according to National Weather Service forecasts.
The El Niño Southern Oscillation (ENSO) phase is one of the most important climate phenomena when it comes to forecasting as well as weather outcomes in a particular place. This is because this has the potential to change global circulation, which then affects temperatures and precipitation.
El Niño occurs when sea surface temperatures in the central and eastern Pacific Ocean, along the equator, are at least 0.5°C warmer than the long-term average. In the last three winters we have seen a La Niña phenomenon, where temperatures have been 0.5°C cooler.
The Climate Prediction Center forecasts that the El Niño phenomenon will occur at a rate of 100% during the month of February. They also have a 73% chance that we will see a strong El Niño. The last time we saw a strong El Niño (+1.5 degrees) was in the winter of 2015-2016.
Here’s what that means for the tri-state:
When the El Niño jet is in its El Niño phase, the Pacific jet stream shifts south from its neutral position, while the polar jet stream moves north. This generally results in warmer and drier winters in areas of the northern United States and Canada, while wetter than normal periods and increased flooding are possible in the southern United States and the US Gulf Coast.
Here in the Tri-State we are stuck in the overall warmer and drier categories. While it would be easy to say that this is how our winter will end, to me this seems like a cop out. Let’s see if we can use past data to see if there are any trends we can follow.
Before we provide a winter forecast, we need to define what a “normal winter” is for the Tri-States. 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, Cincinnati’s seasonal average is 23.5 inches Over the past thirty years. We will use the winter months to determine the average temperature, which is equivalent to… 33.9 degrees. These numbers will be our comparison points.
In the past 30 years, we have had nine El Niño winters, eight neutral winters, and 13 La Niña winters. Below is a list of the nine years with El Niño phases that we have concluded between snowfall and temperatures in those respective years.
Let’s take a look at the climatology of those years and see if we can figure out whether or not there is a trend for El Niño winter outputs here in the Tri-State.
Of the nine El Niño winters, six ended with above-average snowfall, while three ended with below-average snowfall. As for temperatures, five winters ended above normal, while four winters ended below normal.
There doesn’t seem to be a big trend for either, but snowfall is the one that has a bigger trend. But as mentioned earlier, this El Niño may be one of the strongest El Niños ever recorded. Is there a relationship between the strongest El Niño winters and a pattern? Let’s look at all winters with a sea surface temperature anomaly of +1.5°C.
This time there was again a greater correlation with snowfall outcomes, which ended with temperatures six degrees below and two degrees above, than with temperatures, which were four degrees above or below normal. However, of those five recent strong years, four ended with above-average temperatures. The winters of 1965-1966, 1972-1973, and 2009-2010 were the only three winters to have a strong El Niño winter immediately following a La Niña winter. Of those three, all of them ended with below-normal seasonal temperatures.
With all that said, I still think we’re in for a warmer than usual winter with less snow than usual.
I said in my forecast for last year’s winter:
“It is still too early to know if we will see a definitive La Niña event this winter, but if we do, I suspect we will see a warmer-than-normal winter with less snow than usual.”
Last year ended with an average temperature of 38.6 degrees (above normal) and only 14.4 inches of snow (well below normal). Let’s see if we can make it two years in a row!
(tags for translation) 9 On Your Side