March is the snowiest month. We get lots of snow in December. Sometimes it is too cold to snow. When I was a kid (whenever that was) there were more snow storms, the total snow cover was much, much deeper, and when it snowed…it snowed, by golly!
Such are a few of the things people say about the weather. Of special interest to me is the idea that “these days” have less snow than “those days”…according to every one of every age of every region that gets snow.
Have you ever thought this? Have you ever heard this said? If you live in a region that gets snow in a regular basis, and this does not remind you of several conversations you’ve had, then you must be really focused on something because you have not been paying attention.
But is it true? Were winters “those days” more snowy than winters “these days”?
[A revised repost from Quichemoraine.com]
Please keep in mind that none of this applies if you spent key parts of your childhood living in a different part of the country. Like me. Since I moved to Minnesota, winters here have perplexed be somewhat. I’m from the Northeast. As far as I can tell, Minnesota has had exactly two blizzards. One was on Armistice Day in the year 1940 (16.7 inches in the Twin Cities but over 2 feet to the north and 20 foot drifts in Wilmer, 49 dead), the other on Halloween in the year 1991 (37 inches in Duluth, 22 dead). Both involved heavy snow, lots of wind, and other complications (like time of year, time of day, and wet or icy conditions). All the rest of those “blizzards”…nothing more than flurries by Yankee standards! Nonetheless, Minnesotans love their snow, they think they have a lot of snow, and Minnesotans of all ages wax nostalgic about the time, “back then,” when they were around five to fifteen years of age, that there were many, many, many very large snow storms every winter.
So what is the truth about Minnesota weather? How different was your childhood from the present? How do previous Decembers compare to the current one, which has been pretty much devoid of snow, in contrast to one year ago at this time when we had an epic amounts of snow?
Well, I assure you that this has more to do with your psychology than with any climate-based realities. Chances are you think you had more snow as a kid because of two effects; 1) You were shorter. The snow seemed deeper. Well, it was deeper, relatively…and 2) You have conflated several different years, so you are thinking of many snow storms that actually happened over a period of several years as having happened in one year, and thinking of that year as typical. These two effects combined result in your climatological memory of many deep snow falls on a regular basis when you were a kid. But chances are, it never happened.
It is possible that it did happen. It is possible that you remember a few years that happened to have a lot of snow falls, and a lot of them were heavy. We can investigate that. But first, you need to do something. You need to lay down the facts of what you think is true, prior to looking at the data. So, here’s three questions I have for you:
1) How many inches fall before you can call a storm a large snowstorm? Three? (That seems kind of wimpy.) Four? (Really? Four? Seriously?) How about six. Six inches or more is “a lot of snow.” OK, that is just a suggestion. You pick whatever number you want. Write it down. I’m going with six.
2) How many snowfalls of that size per year is “a lot of snow” or “snow like I remember it” or whatever. You have most snow falling during December, January, February, March. So, over four months how many snow falls of the size you think is “a lot of snow” seem, according to your memory, to have fallen? One per month for a total of four? Huh. You think that’s a lot? Does not sound like a lot. How about two per month. That’s not many, but it adds up. Three might be too many. That would give you 12. Maybe you’d pick ten. Eight to ten snow falls over 6 inches in a given season (including the aforementioned four months as well as October, November and April, just in case). If you picked these numbers, your idealized Wayback Winter would have had a minimum of eight storms of six inches each. Maybe those are your numbers. Maybe you’ve got different numbers.
Whatever. Write it down.
3) How much snow was on the ground in December in your idealized Wayback Winter? Total. If there were two big storms, that could have put 12 inches on the ground by the end of the month. That sounds like a lot, but maybe that’s what you think. Maybe you’ll be conservative and say something like six. Six inches of snow fallen from the sky in the month of December, unmelted. Or some other number? Whatever. Write it down. I’m going with six inches.
OK, let’s look at the facts. The following data are for the Twin Cities region of Minnesota.
How much snow falls per month? Is March really the snowiest month?
March is not the snowiest month. There are a lot of ways to look at this, but one source suggests that the snowiest month is January, with March the second snowiest. After that, it’s December (third snowiest), February, November, April, then only trace amounts in some of the other months.
How many storms of X inches do we get per year?
Let’s say you were born in 1984 and lived in the Twin Cities since then. You imagine that winters were snowier “back then” when you were little. Given the above discussion, you’ve decided that a “snowy winter” meant six inches were on the ground at the end of December and a total of six storms of five inches or more happened during the entire winter season. Notice that your estimate has become more conservative than what you made above, because you are staring to learn that I rarely write blog posts that confirm your preconceptions, especially when I’ve tricked you into having a particular preconception.
Anyway, this would all be in contrast to “these days” when we seem to have vast periods of time with no snow at all, bare exposed ground through much of December, and hardly any big storms.
So, let’s contrast “these days” (say, 2005, 2006, 2007 and 2008) with “those days” (say, 1987, 1988, 1989, 1990).
Here’s the numbers. For “these days” there were no six-inch-plus storms in 2008, and only one each in 2005, 2006, and 2007. Pitiful. The occurrence of five-inch-plus storms was four, three, one and one; the occurrence of four-inch-plus storms was four, three, four and one. In other words, the total number of storms per year that are six inches or more currently is fewer than one on average, and if we drop our standards to four-inch storms, the average number per year goes up to a pitiful three. Wow that’s way less than our memory, which is something like six storms of five inches or more.
Now lets compare “these days” to “those days” using the aforementioned years.
The number of six-inch storms in 1987, 1988, 1989 and 1990 were zero, one, two and zero. That is the same as “these days” in that the average number of six-inch storms then and now is 0.75 per year. When we look at five- and four-inch storms, it’s worse… the total number of each type of storm is less during “those days” than during “these days.”
So, given this particular comparison, the idea that there was more snow…more storms and more snow in at least some of those storms…is wrong. That is a meteorologically reconstructed memory. Which is why we use science, and not culture, to characterize and study the weather!
Indeed, the total number of storms for these four-year periods is roughly what some of your reconstructed memories of the past could have attributed to a single year.
But wait, I could be making this up! I could have picked years that happen to be lean from the past. Why DID I pick those years anyway? Well, I’ll tell you. Those are the years that would have pertained to a particular person I was talking to about this the other day. But it is true that different years could give different results.
It turns out that if I had shifted the “back then” years by one, to include 1991, then the year of the great Halloween Blizzard would have been included. That year included several large storms, not just the Halloween storm. However, if I re-calculate the averages over four years including 1991 and dropping 1987, those averages become more like “these days” but do not significantly exceed them. If the Halloween Storm is part of your childhood memory, that does not mean that winters were generally snowier “back then”…but that particular year would be a source of memories of big storms and more storms that you could then use to fill in the other years that are actually rather pitiful in snow storm frequency and snow storm amounts.
If you still don’t believe me, you can do this experiment. Before looking at the data, if you are a Minnesota resident from around the Twin Cities, pick the four or five years that would best represent your youthful memories. Then, go here and select those years, select “snow” and compare. If you find a youth with a lot more snow storms and a lot more snow per storm, report back, we want to know!!!
Was December snowier “back then?”
Not according to the data I obtained in the comparison outlined above. The average number of inches on the ground at the end of December for the “these days” period and the “back then” period is the same. Four.