Another summer has come to a close… and for many of us, it ended much too soon. Those warm, sunny, days at the beach… those dog days of summer… have passed us by. But with the end of the summer each year, our eyes turn to toward the winter, as we begin to speculate on what may be coming our way. So it has become a tradition, that we issue our annual “HVW Winter Outlook”.
Over the last several years, we have observed and studied many methods of long range winter forecasting. Some methods are based on science, and others are a bit more experimental in nature. What we’ve done, is combine some of the methods that we feel are most effective, and use them to project the pattern for the upcoming winter season. When we discuss the winter season, we are generally talking about the period from December through February in terms of temperatures, and first flake to last flake in terms of snowfall. So lets dig in, and take a look at the 2017-2018 HVW Winter Outlook.
Winter Temperatures : Near Average to 1.5° Below Average
The tropical Pacific Ocean is beginning to head into a La Nina, and that his historically meant a cooler than average winter in the Hudson Valley and Northeast. It has also resulted in winters that get off to a quick start in the month of December, and we think that is possible with a near to below average December expected. Last December was right near average, thanks to cold shots that were quickly repelled by a rebounding warm SE ridge. This December, we think the cold air may be able to hit and hold a bit better during the month of December. January looks likely to feature a lot of ups and downs in terms of the temperatures, as cold Canadian air battles for position against the warmer air in the southeast. Depending on how things turn out, January could actually end up a bit warmer than normal. February could end up being the most active in terms of winter storms, as the Canadian air should persist over the eastern US.
All said and done, the potential temperature range this winter is rather large. The La Nina usually translates into a cooler than average winter for the northeast. But when we factor in the waters in the northern Pacific, the result suggests that our cool winter could become quite a cold winter. We’ll have to wait and see.
Winter Snowfall : 45 inches to 65 inches (90% to 133% of Average)
With temperatures projected a bit colder than average, there should be plenty of opportunities for snowfall this coming winter. The average annual snowfall in Poughkeepsie over the last 25 years is 49.6″. Our projection for 45″ to 65″ may seem like a wide range, but annual snowfall totals are often a matter of ‘luck’. We’ve had cold winters with below average snowfall, and mild winters with above average snowfall. The reason is because snowfall is all about the timing. As simple as it may sound, you need the cold air in place when the moisture moves in.
This winter, we anticipate that luck may favor the snow more often than not. You’ll notice this map shows below average snowfall for much of the eastern half of the country. However, notice the above average snowfall in the northeast… consistent with a pattern you would expect as a result of nor’easters. We think that the pattern for much of this winter could favor coastal storm development. With that coastal development, comes the potential for heavy snowfalls, and that adds even more uncertainty to the snowfall totals.
So now that we’ve outlined our expectation for the winter, let’s discuss how we arrive at those ideas. We combine a variety of factors to create our Winter Outlook. The ENSO state (El Nino – Southern Oscillation) is a major factor, as well as the rest of the sea surface temperatures across the Pacific and Atlantic Oceans. In addition, 2017 has been a very active hurricane season. So we analyzed the most active Atlantic Ocean hurricane seasons according to a measurement known as the ACE index. ACE or Accumulated Cyclonic Energy, measures more than just the number of storms in a season, it focuses on the cumulative energy of tropical systems within the season. With an ACE of 227 on the season, 2017 is currently the 4th most active season since 1949 (since Poughkeepsie has recorded data). By comparison, an average season to date would have an ACE of 96.
So lets start with the current sea surface temperatures across the Pacific Ocean…
As of October 6th, these are the sea surface temperature anomalies across the globe. We’re going to focus on 3 specific areas in the Pacific Ocean, which we highlighted with A (ENSO), B (Eastern Pacific), and C (North Central Pacific). These 3 areas create a pattern that together should help define the general weather pattern this winter. Above is the current sea surface temperature anomaly, lets look at what the models are projecting for the 3 month period of December, January and February…
You’ll notice, that the forecasted sea-surface temperatures for the winter months are similar to the current conditions… with a few differences. The forecast is for the La Nina (cooler than average waters) in the ENSO region (A) to strengthen. The waters in the northeastern Pacific (B) are projected to cool a bit as you move into the Gulf of Alaska. And the waters in the central Pacific (C) may moderate just a touch, but should still be cooler than average.
So we have taken a blend of the current sea-surface temperatures, and the forecasted temperatures this winter, and began to search for years where the conditions were similar. We analyzed all the winters from 1949 to the present, and selected the years that best fit the expected pattern. The selected winters are considered analogs to what we expect to see this winter, and came up with 11 seasons in total. We then weighted them based on how closely they resemble the pattern we anticipate. Here is the sea-surface temperature pattern that results when we blend all those winters together…
Notice that the areas we highlighted are very closely aligned with both the observed current sea-surface temperatures, as well as the forecasted sea-surface temperatures this winter.
Then we decided to cross reference the most active Atlantic Ocean hurricane seasons.
With 2017 being one of the most active on record, we wanted to see if there was a correlation between active Atlantic hurricane seasons, and the sea-surface temperature pattern we’re seeing. And as it turns out, 2 of the 3 most active Atlantic Ocean hurricane seasons on record (in terms of ACE), were part of our original 11 year analog package. Even more note worthy… those two winters… the 1995-1996 winter, and the 2005-2006 winter, were the two highest weighted seasons of the 11 analog seasons.
So to bring it all together, and to generate this year’s winter temperature and snowfall outlook, we combined our sea-surface temperature analog package, with the most active Atlantic hurricane seasons, to come up with this Winter Outlook:
What will we actually see this winter? Well, only Mother Nature knows for sure. But based on historical trends and a bit of scientific reasoning, we think a chilly and rather snowy winter is likely. Only time will tell if our reasoning is sound, but we can already see things playing out according to plan. Here is a graphic showing North America after the first half of October…
Notice how warm the eastern half of the country was in the first half of October. Poughkeepsie itself had measured a full 8°F above average half way through the month, and finished the month 7.5°F above average. So we took the strongest analog years of 2005, 1995, 1985, 1983, and 2016… and asked what those Octobers looked like. Take a look…
The seasons that most closely resemble what we anticipate for the coming winter, also contained very warm Octobers. So if you’re looking for an indicator of whether our winter outlook may be on the right track, there you have it.
But no matter the result, we hope you enjoyed taking a look at the possibilities for this coming winter. Thank you for all the amazing support you have given to us at Hudson Valley Weather. We look forward to guiding you through all of the adventures this winter has to offer this season.