It’s tough enough to predict in November what winter will be like. There is established science on this: El Nino and La Nina, NAO and AO, PDO and QBO, plus Siberian snow, and others. The past two winters haven’t even seen the methods using the above items turn out. “Some weird and wild stuff,” as Johnny Carson used to say (showing my age).
But it’s always interesting to get a good question and be inspired to do some research to find an answer. Our memories are bad and biased, so we just can’t go by: “It seems that mild starts to winter end cold and snowy.”
Instead, Dave Warren and I looked back at more than 130 years of detailed records for the Philadelphia area. We first looked for ALL seasons that had well above average temperatures for December and January, PLUS less than 8 inches of snow. There were about 20 of those. We then looked at what happened in the months to follow. Did the warm weather continue? Was there a big change? How much more snow fell that season? And, is there any trend for spring rain?
I’ve always enjoyed research projects like this. In college, I researched the forecasts from The Old Farmer’s Almanac from more than 50 years, and found their forecasts were worse than flipping a coin!
Then, while working at The National Hurricane Center, I did extensive climate research on Miami and discovered that the addition of wide-body jets around 1970 had raised nighttime temperatures significantly. Since the airport is the official weather observation site for Miami, weather history changed because of a bigger airplane!
So, you can see that climate research can lead to some answers about the future. Not absolute answers, but finding a change in the odds. We don’t have enough precise data for a really good view of the odds-I would prefer 1000 years of record instead of the 130 we have.
Those 22 mild, non-snowy starts to winter started showing some trends. Only 5 of them continued the trend of significantly above normal temperatures for February and March. Usually, at least one of those months had significantly below normal temperatures. Very few had a lot of snow.
There appeared to be a trend. Next, I threw out all El Nino winters (we’ve had a significant La Nina all winter, which is expected to continue through the spring). This led to even better odds of a cooler than normal March and/or April, and even less snow.
This is not to say that it must get colder and that we have to get more than 6” of additional snow. It just means the odds are skewed in that direction. In 2001-2002, for example, we followed a very mild January with a very mild February, March, and April, and we had NO measurable snow in those months. So, it can happen.
As for rain, the La Nina springs stood out with generally wetter months, especially March and May. At least one of those months was very wet each of those years.
The overall global weather pattern will determine how our spring turns out. The Arctic and North Atlantic have been very unfavorable for the type of blocking patterns we saw in the past 2 winters. In fact, it’s been almost the opposite pattern. It’s no coincidence that much of the country has seen mild temperatures and very little snow. The upper-air patterns for the next 10 days show the same pattern:
Instead of big areas of high pressure near the North Pole and Greenland, there is low pressure. So, if the pattern is going to change, it won’t be until at least the end of the month. But the pattern changed in a hurry in Europe in the past 2 weeks, so that kind of thing is possible. You can be sure I’ll be watching the Arctic and the North Atlantic for signs.
Fan, follow and download: Get the latest from NBCPhiladelphia.com anytime, anywhere. Follow NBC10 Earthwatch on Facebook. Sign up for our weather newsletter. And, get weather forecasts delivered right to your mobile phone -- just text PHIWEATHER to 639710 to sign up. (Message and data rates may apply.)
