Another mild day for December 27th was the third in a series of unusually warm afternoons here in late December. The records in Boston show that we have seen a 50F degree reading or higher 15 times since the late 1800s on this date. One of those occurrences was 1888 when it reached a balmy 57F and another was 2011 when it hit 56F. Today, Logan Airport hit 52F this afternoon for the 16th time Boston has reached this milestone 4 days prior to the end of the year.
One thing you might be thinking, now meteorological winter is nearly 1/3rd over, is will the rest of the winter be this easy? First of all, no one knows for sure what the next 3 months has in store. Even the most modern and sophisticated of computers, which can look at historical data to help predict the past, won’t tell us with certainty if Boston will reach 20, 30, 40 or 50 inches of snow by the end of winter. But, there are some data points we can look at to help predict the rest of the winter and I don’t think snow lovers are going to like it.
El Nino
There are all sorts of ways to think about the rest of the winter in terms of cold and snow. The one piece of data we do know is we are in now or about to be in a weak El Nino. These events are kind of like a recession (you need multiple quarters of negative growth) in that you need consecutive weeks of warm ocean water in a certain part of the Pacific off the coast of Peru. In other words, a week or two of warm ocean water doesn't mean you have an El Nino. More on that in an upcoming blog.
It's a good bet this season’s El Nino won’t be as large as others we have seen in the past. The loop below shows how ocean temperatures are behaving over the past couple of months.
With this in mind, I set out to see what has happened in the past when Boston has seen very little snow in December. For the purposes of this blog, I considered all the Decembers in which Boston recorded 2 inches or less of snowfall. What I found is that most of the rest of the winter didn’t bring enough snow to produce an above average amount for the entire winter. However, and this is important. The average snowfall for January through the end of the season for those 25 winters was about 30 inches. This means even though we haven’t had much snow yet, we are still likely to have several snowy weeks ahead. Additionally, if we ended up with 30 inches of snow it would matter a lot how it fell. Three storms of 10 inches each would be a lot more tolerable in many ways than having ten snow events of 3 inches, all during the morning commute.
Historical Evidence
Some years like 1926 saw a lot of snow in one month. That year over 27 inches fell in February. Many forecasters were predicting an above average amount of snow this year in Boston, at this point I think that is becoming increasingly less likely and what’s more likely is a year with 20 to 30 inches of snow in total. I think the odds of a winter under 15 inches of snow and over 50 inches are both quite low.
Worcester Snowfall
Below is a chart of Worcester snowfall for the 22 lowest December snowfall's on record. Notice how many of these years ended up with below average snowfall. In Worcester average is about 70 inches. Again, like Boston, low December snow raises the odds the rest of the winter won't see blockbuster snowfall. I put a red oval around the two years when snowfall was low in December and was followed by a lot of snow the rest of the season. Like most of meteorology there are not many rules that are 100% true all the time.
I think the first 10 days of January is going to be critical in determining whether a colder and snowier pattern can become established.
Could this winter end up like 2002-2003 (above) when January started warm and wet and ended up as one of the coldest in decades followed by a whopping 40 inches of snow in February or will the signs I am seeing thus far continue and the predictions of a snowy winter fall far short? You can be sure I am going to be looking at each bit of data with a lot of interest and I’ll let you know as soon as I do. Follow me on Twitter @growingwisdom for the latest data and feel free to send me your comments there. Have a great weekend.