As November begins questions about the impending winter are common. All of us would love to know what type of winter it’s going to be, not so much because we can do anything about it, but because there’s something psychologically comforting about knowing what’s ahead.
If I could tell you with certainty this was going to be a very cold and snowy winter, or a wet and mild one or a dry and cold one at least you could mentally prepare. The reality is that even the best climate forecasts can be wrong and the best forecasters will not predict the winter correctly.
The atmosphere is exceedingly complicated. However, there are some variables that do have somewhat predictable outcomes here in the Northeast. For example, in strong El Nino years, Decembers tend to be much milder than average. This was the case last winter. Even if there were other factors pushing the atmosphere colder last December, the El Nino variable overwhelmed everything else and gave much of the country unusual warmth. This remained the case all winter long.
Keep this in mind throughout this winter. Throughout the next six months I will continue to look at which variables are most likely going to influence our weather in the short and long term. These variables, such as the Pacific Decadal Oscillation, the North Atlantic Oscillation, the Arctic Oscillation, Maiden Julian Oscillation, warm and cold blobs of water in the oceans, sun intensity, stratospheric temperatures and more, are like switches helping to push the atmosphere in various directions. Sometimes the switches contradict one another and other times they are more aligned.
What makes a winter memorable isn’t necessarily if it’s above or below average with temperatures and snowfall, but how and when the snow piles up and how long the cold lasts. Do you think many people remember the winter of 2015-16 brought one of the coldest 24- hour periods since 1957 for parts of New England? Overall the winter was exceedingly mild with very little snow in most areas compared to long-term averages. It was the warmest December-to-February period, in spite of the weekend of extreme cold.
Nearly all of us remember the onslaught of snow and cold in 2015. However, the big snows of two years ago didn’t even begin until meteorological winter was half over! A few weeks of extreme weather can destroy any long-range forecast’s accuracy really fast.
Most forecasters agree this winter will be more typical along the East Coast. Scientists, such as Judah Cohen, a research climatologist at MIT, use snow cover across Siberia to predict the upcoming winter. This method does have some validity, but was quite poor last year when the El Nino kept things very warm in spite of early Siberian snow cover. Snow cover is higher than average in much of the northern Hemisphere this year.
The past 10 months have been exceedingly warm here in New England with all but one month, April, being warmer than average. There are models that continue this trend, but a warmer than average winter doesn’t mean it won’t be cold or snowy. Remember, December through mid-March is generally cold, so even if it’s a bit above average in terms of temperature we can still see a lot of snow.
Drought years are also not necessarily low snow years. The summer of 1995 was one of the drier on record and that was followed by over 100 of inches of snow in many New England cities including Portland and Boston. If we had light fluffy snow all winter and it melted to just half the normal precipitation, we could still have a snowy winter. On the other side, if all our storms were heavy wet snow, precipitation (melted snow) might be high, but snow totals would be lower.
Are you getting the idea the long-range winter forecast is a combination of science, experience and a some guesswork? That is true. You can likely find a forecast to support whatever you are hoping for this winter. Take all of them with a grain of salt and keep the shovels closer to the front of the garage. The folks at WeatherBell Analytics are quite bullish when it comes to snow this winter. We shall see.