As we go into the winter season, it’s time to talk about how this one might end up. There’s a belief that fall weather is a good sign of how cold or warm winter will be. How true is that for Columbus? Also, what might any correlation mean for the winter of 2017-2018?
First, let’s just look at October temperatures.
The October normal mean temperature for Columbus is 55 degrees.
Between 1878 and 2016, there have been 47 Octobers that featured a mean temperature of 53.9 degrees or lower, what we’re considering a Cold October for the purposes of this comparison.
Of those 47 Octobers, 27 of the 47 had following winters that were colder than normal, or 57.4%, 13 had average temperature winters, or 27.7%, and the remaining 7 were warmer than normal, or 14.9%.
Interestingly, this category contains both the warmest winter on record- 1889-1890 and the coldest on record- 1976-1977- as shown by the chart below.
Next, we look at Normal Octobers, which are +/- 1 degree of the 1981-2010 Average of 55 degrees.
Between 1878 and 2016, there were 45 normal Octobers. Of those, 21 had colder than normal following winters, or 46.7%. 11 were followed by normal winters, or 24.4%, and 13 had warmer than normal winters, or 28.9%.
Finally, let’s look at warm Octobers, which are those with means of 56.1 degrees or higher. There were 46 Octobers with warmer than normal means since 1878. Of those, 18 featured following winters that were colder than normal, or 39.1%. Another 18, or 39.1%, were followed by average winters. The final 10 winters were warmer than normal. Here’s the graph.
So just based on the October mean temperature, Octobers that are colder than normal have a 47% higher chance of having a colder than normal winter than warmer than normal Octobers do. But is October a better indicator than November, a month that is closer to actual winter?
Colder than normal Novembers- 43.3 degrees or lower- included 78 Novembers since 1878. Of those, 38 or 48.7% had colder than normal winters. 21 (26.9%) had normal winters and 19 (24.4) had warmer than normal winters.
Finally, there were 24 warmer than normal Novembers since 1878- 45.5 degrees or higher. Only 6, or 25%, were followed by cold winters. An additional 9 (37.5%) were normal, while the last 9 (37.5%) were warmer than normal.
To reiterate, here are the ranked percentages of cold winters by the preceding October or November.
1. Cold Octobers: 57.4%
2. Cold Novembers: 48.7%
3. Normal Novembers: 47.4%
4. Normal Octobers: 46.7%
5. Warm Octobers: 39.1%
6. Warm Novembers: 25.0%
It should be no surprise that cold Octobers and Novembers have a stronger correlation to the following winters also being colder, with colder winters becoming increasingly unlikely as those months warm. Cold Octobers have a higher correlation than Cold Novembers, as well as Warm Octobers, but Normal Novembers have a slight advantage over Normal Octobers. Based on this, October actually has a stronger correlation to the following winter’s temperature mean than does November.
Going further, though, what about bi-monthly combinations?
Rank of Bi-Monthly Combinations and the percentage of colder than normal following winters, along with total years in sample:
Normal October/Normal November: 87.5% 8 Years
Cold October/Warm November: 57.1% 7 Years
Cold October/Cold November: 53.8% 26 Years
Normal October/Cold November: 48.1% 27 Years
Warm October/Cold November: 44.0% 25 Years
Cold October/Normal November: 38.5% 13 Years
Warm October/Warm November: 28.6% 7 Years
Warm October/Normal November: 26.7% 15 Years
Normal October/Warm November: 0.0% 8 Years
So a normal fall is clearly the best, but the sample size is not particularly high. Normal to Warm is unanimously warm, but again, it has a small sample size.
October 2017 has been overwhelmingly warm. While this wouldn’t normally bode well for a cold winter, each year is influenced by a multitude of factors.