How much juice does our snow produce?

At Caribou, by Halloween, the average high will be down to 45 degrees and the average low will be below freezing, at 30. It’s a bit shocking how quickly we descend into our colder time of year. But the REAL shock will come four days after Halloween, when we roll back the clocks by an hour, and the sun starts setting around 4:15.

And then, before long, the flakes will fly, which, for our winter economy, is a very good thing.

Can we get October snow? Sure can. Back in October 1963, Caribou saw just over a foot for the month, the bulk of which was associated with Hurricane Ginny, which passed over southwestern Nova Scotia. Then, famously, back in November 1974, Caribou had almost 3 feet, with a lot of that falling in the days leading up to Thanksgiving.  Longtime County residents will remember that November vividly. In fact, November ’63 was the snowiest month of that entire winter.

So obviously we know that we have long winters here in The County, with snow on the ground for a good hunk of the year, but the question is, what percentage of Caribou’s average annual precipitation (rain plus melted snow) falls, initially, as snow?

First, let’s make a reasonable assumption, that 10 inches of snow melts down to 1 inch of water. Individual storms can feature fluffier snow (one inch of water would yield more snow), or the snow can be heavy and wet (one inch of water would yield less snow). But just shooting for a fair average, we’ll call it 10-to-1. By the way, fluffy snow is called “high ratio” snow, whereas heavy, wet snow is called “low ratio” snow.

Here are the things we need to know to find out snow’s contribution to our annual precip total: Caribou’s average annual total precipitation (rain plus melted snow) is about 38 inches.Caribou’s average annual snowfall is about 109 inches.

In order to figure out the percentage of total precipitation that falls as snow, we need to compare apples to apples, so we need to turn that 109 inches of snow into water. Using our 10 to 1 ratio, that 109 inches of snow melts down to 10.9 inches of water.

Next we get to use what for many is a four-letter word, MATH. There is a nifty way to figure out a fourth thing, when you know what the first three are. And indeed we do know the first three. Here they are: we know that 38 inches (1) is, on average, 100 percent (2) of the total precipitation Caribou receives. We also know that snow contributes 10.9 inches (3) to that total. What we do not know is, what percentage is that 10.9 of the 38 inch total? So a nice math trick to figure this out by hand (do it with your children or grandchildren) is called cross-multiplication. And if you struggle with math, it’s best to sound it out as you go.

Let’s do it together. If 38 inches is 100 percent of the total (write on a pad, 38/100), then 10.9 inches is what percentage of the total? (write on a pad 10.9/x). Now place an “=” sign between the two fractions and cross multiply, which is numerator of the first fraction times the denominator of the second (put that on the left side of the “=” sign), then numerator of the second fraction times denominator of the first (put that on the right side of the “=” sign).  What you get is 38x = 1090. Divide both sides by 38 to isolate x, and you find that x equals 28.6. You have just found out the Caribou’s average snow contributes a bit more than one-quarter (28.6 percent) of the annual average water received. I’ll bet that’s somewhat less than you might have thought.

A final note: at this writing, we are waiting for first light, to more fully assess the destruction wrought by Hurricane Michael, which made landfall on Oct. 10 just northwest of Mexico Beach, Fla. Michael was the third most intense landfalling hurricane on record, with a central pressure of 919 mb (27.14 inches). The lower the pressure, the more intense the hurricane in terms of maximum winds. The most intense landfalling hurricane on record is the Labor Day Hurricane of 1935 in the Florida Keys. It had a pressure at landfall of 892 mb. Hurricane Camille in 1969 made landfall on the Mississippi Gulf Coast with a central pressure of 905 mb.

Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been chief meteorologist at WAGM-TV since 2006. Email him at tshapiro@wagmtv.com.

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