A third straight winter of La Niña conditions is expected, according to The Climate Prediction Center (CPC).
The phase of the El Niño-Southern Oscillation (ENSO) is one of the most critical climate phenomena regarding forecasting and the weather’s outcome in a given location.
This is because this can change the global circulation, which then impacts temperatures and precipitation.
A La Niña is when the sea surface temperature along the equator in the eastern Pacific Ocean is at least 0.5°C cooler than the long-term average. We have seen that during the last two winters.
As you can see in the graph above, we have remained in a La Niña pattern for much of the last two years exceptfor a few months in the mid of 2021.
Right now, the probability of a La Niña looks to be at least 60%, if not higher, through February. If this happens, this would only be the third time in the last 73 years where we had three straight winters of La Niña conditions. The only other times this has happened were in the mid-1970's, late 1990s, and early 2000s.
What Does It Mean For The Tri-State?
When ENSO is in a La Niña phase, it usually leads to the Polar Jet Stream shifting further to the south, bringing colder temperatures to the northern United States. Here in the Tri-State, that southward shift in the Polar Jet Stream generally leads to a wetter winter pattern.
While it would be easy to say that is how our winter will wind up, that 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.
Something to ponder is what a normal winter brings to those of us in the Tri-State. While the winter months are defined as December, January, & February, we can see snow from October through April.
So when it comes to snowfall, the seasonal average for Cincinnati has been 23.3 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, nine Neutral winters, and 12 La Niña winters. Below is the list of the 12 years with La Niña phases and where we finished among snowfall and temperatures.
Of those 12 winters, six finished above average in snowfall, while six finished below. Regarding temperatures, seven finished below normal, while five finished below normal. That doesn’t lend itself to a trend one way or another. However, this winter is a little different because it will be part of a consecutive La Niña season.
Among the winters listed above, five such occasions had back-to-back (even one instance of back-to-back-to-back) La Niña. All five of those winters ended with below-average snowfall, and three of the five finished with an above-normal temperature.
It is still too early to know if we will definitively see a La Niña this winter, but if we do, I will suspect that we see a warmer than normal winter with below-normal snowfall.
If we switch into a Neutral Phase, that would change things quite a bit and likely lead to a colder than normal winter. We shall see!