Crozet Weather Almanac: November 2012
A Cold November Tends to Last
By Heidi Sonen and Roscoe Shaw
November was cold. Very cold. The month averaged a full four degrees below normal, making it the ninth coldest November here in 100 years. It didn’t seem so bad, though, because the month was mostly tranquil and dry, with generally nice weekends.
“So, Heidi and Roscoe, what kind of winter are we going to have?” We can’t make it in and out of the Great Valu without getting hit with that question. The simple answer is that we don’t have a clue. Long-range forecasting of temperature is still pretty pitiful and precipitation is next to impossible.
This is not for lack of trying. The economic benefit of long-range forecasts would be fantastic. But for the most part, success has been elusive.
Don’t even start with the Farmer’s Almanac. They just make that stuff up because people want to read it and have been buying it for 250 years. The writing and phrasing are clever but the scientific skill is ZERO. If you are one of those people who insist the Almanac gets it right, then please talk to us about something else at the supermarket.
This year, everybody keeps asking about the plethora of acorns. What does that mean? Well, unfortunately, nothing. How about Wooly Worms? They are a big deal for some reason in the mountains of North Carolina. Appalachian State University actually once did a long study where they collected many samples and analyzed the results with multivariate regression analysis. Nothing!
But, we aren’t completely clueless. Turns out that the best predictor we know of in the eastern United States for the coming winter is the November weather. If it’s cold in November, then it tends to be a cold winter and vice versa. That’s what is called a “persistence” forecast. Most of the time, it doesn’t work. But for the last 100 years, it has been a reliable indicator of the coming Virginia winter.
So, the cold November this year means that we have a 70 percent chance of a colder than normal winter.
But what does this tell us about snow? Snow in Virginia is a near-random event. A cold winter is not necessarily a snowy one. To get snow, we just need a couple of good storms to come together just right. That can happen even in a warm winter or fail to happen in a cold winter. The November predictor doesn’t work for snow and I don’t know anything else that does either. So, we’ll just have to wait and see.
If you are a snow-lover, then prepare to be disappointed. We average 18 inches of snow a year but oddly, half the years get less than a foot. “That’s not possible,” you are thinking. But it’s true. Half the years get less than a foot but sometimes we get 40 or 50 inches in a winter and that pushes the average up to 18.
November was remarkably dry, with the only significant rain coming on the 13th. Normal rainfall for the month is 3.57” but we were 80-90 percent below normal. The growing season is over so this wasn’t much of a problem, but we will need to recharge the groundwater at some point this winter or face the possibility of drought next summer.
- Greenwood 0.68”
- Charlottesville Airport 0.45”
- Crozet 0.47”
- Waynesboro 0.73”
- Univ. of Va. 0.82”
- Nellysford 0.82”
- Rockfish 0.42”
- Afton Summit 0.55”