How to assess which long-term winter weather predictions are reliable – The Washington Post

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Throughout history, people have sought signs of the winter to come, turning to the skies, the land and the water. Will it be mild or cold? Snowy, rainy or dry? People watch the behaviors of animals and plants, clouds, oceans, and in recent decades, computer models to drop hints about the winter to come. After all, knowledge is power, and any advance warning of severe winter conditions or mild ones can let people prepare in advance.
But who can you trust when it comes to winter look-aheads, and which ones are best left to the entertainment department? If you are making decisions based on winter outlook information, you might want to consider relying on tested methods from experts — not a farmer’s almanac or caterpillar.
How harsh will winter be? Six organizations issue forecasts.
The National Weather Service’s Climate Prediction Center
Every month, the National Weather Service Climate Prediction Center sends an outlook for the 12 upcoming three-month “seasons,” with maps that paint areas favored for temperatures to be unusually warm or cold, and precipitation to be unusually wet or dry.
The outlooks are given as odds, tilting those odds toward a favored category the same way that weighted dice can favor one roll over another. CPC never forecasts a guarantee or predicts specific temperatures or precipitation amounts. The inputs to CPC outlooks are known and based on published methods. The verification, where they compare forecasts to outcomes, is public and adds credibility to their methods and results.
The outlooks lean heavily on climate change trends, the influence of El Niño or La Niña, and some longer-range computer models, but very few global patterns have been confidently connected to the winter ahead when looking more than a month in advance.
Interpreting the outlook maps can be challenging. If you want to dig deeper, the National Weather Service has training to help.
Research groups
A handful of other research-based entities produce seasonal or sub-seasonal winter outlooks. One of these, the International Research Institute for Climate and Society at Columbia University, partners with the CPC to extend seasonal outlooks, including winter outlooks, to a global perspective. The experts in both groups collaborate to make the forecasts, sharing their collective expertise in a decades-long partnership.
Another entity providing winter look-ahead information is Verisk Analytics, a private company, largely through the work of one scientist: Judah Cohen. While Cohen’s work is done for a private company, he does publish his methodology. Many of his methods are still being tested and debated by climatologist peers — something he invites with weekly discussions.
Winter’s coming: Here’s what to know about long-range weather outlooks
Traditional Indigenous knowledge
Indigenous peoples around the globe have been tracking winter weather patterns for generations, passing on their knowledge in writing and pictures, or orally through their own traditions. Until recent years, the methods of Western scientists have remained independent from traditional Indigenous knowledge. As these scientists connect with Indigenous knowledge of the environment and ecology, they incorporate viewpoints not considered in the past.
The connections with traditional Indigenous knowledge are new and, in some cases, delicate, as Western scientists learn to navigate relationships with and become trusted by Indigenous peoples.
Almanacs
What does it mean to say a winter will be “cold, snowy” for a three-week period in February, especially in snowy climates? Is one snowstorm enough? How cold does it have to be to qualify as “cold” in the almanac? These questions are among the many reasons that validating the farmer’s almanacs is next to impossible. The language is too vague, applies to too large of an area and too long of a time, to assign a “hit” or “miss” to the outlook.
According to the Farmers’ Almanac, the outlooks rely on a formula that considers sunspot activity, the moon’s tides and positions of the planets, but the authors do not publish or publicly discuss their methodology, leaving the scientific community in the dark about their validity. Although the Farmers’ Almanac states forecasts are 80 to 85 percent accurate, closer, independent looks at the outcomes demonstrate that the almanacs are, at best, the same as flipping a coin.
Groundhogs
Punxsutawney Phil and his prognostications are the subject of an unofficial holiday, a movie and a large gathering of suited men proclaiming whether winter’s end is close. By legend, the groundhog who sees its shadow gets scared back into its hidy-hole for six more weeks of winter, while the one who does not see its shadow emerges and winter’s end is nigh. Unfortunately for Phil’s fans, he’s worse than a dart board at predicting the end of winter. Take the National Centers for Environmental Information’s word for it — the groundhog is not a forecaster.
Woolly bear caterpillars
Woolly bear caterpillars are often credited with the ability to forecast winter seasons by the thickness of their brown and black stripes, with thicker black stripes foretelling a longer, harder winter. But their stripes have nothing to do with the weather — their width stems from how long the caterpillar has been feeding, its age and its species. Woolly caterpillars that crawl south don’t predict a hard winter, nor does northward movement indicate a mild winter — their movement is directed by finding shelter under a rock or some bark, or perhaps a tasty treat.
Acorns
Legend holds that years with lots of acorns falling from the oak trees (“mast years”) are those that bring hard winters, providing extra food for the squirrels, chipmunks and other gatherers. Instead, it turns out that mast years are more tied to the weather of the past season than the future one. Oak tree flowering in the spring depends on the temperatures in the winter and early spring leading into flowering season. Mild winters without a deep spring freeze are more favorable for flowering, which translates to more acorns developing.
Geese
While geese migration patterns can foreshadow shorter term weather, they are not a sign of the winter to come. Geese can fly high in high-pressure weather, when the denser air allows them to loft more easily. On the flip side, they tend to fly low in low-pressure weather, which typically brings more unsettled conditions. Geese may migrate just ahead of a cold front, foreshadowing the arrival of a cold-weather spell. But cold weather in fall does not foretell the entire winter to come.
Local television meteorologists and private companies
Some local meteorologists and private weather companies release winter outlooks, often without fully explaining their methods. If the methodology isn’t known, then it can’t be tested by other scientists to check its accuracy. If the outlook details are described using words rather than degrees and inches, then their accuracy is difficult to evaluate. Some local meteorologists and private weather companies employ a sound and transparent methodology for their outlooks, but others do not. Use with caution.
Other animal behaviors
Not every relationship between animal behaviors and the winter ahead has been tested, so it would be irresponsible to say that they all are mythology. It is unlikely that any one animal or plant holds the key to the winter ahead.
Researchers need to conduct more research to fully understand the relationship between some animals’ behavior and the environment. Such animal behavior will be better understood as Western science better connects with traditional Indigenous knowledge to tune into the long history of observations and understanding held by Indigenous peoples.
Barb Mayes Boustead is a meteorologist and climatologist living in the heart of the Great Plains. Her interests include the overlap between weather and climate, especially in weather extremes, as well as historical weather events like the one at the heart of Laura Ingalls Wilder’s “The Long Winter.” She is a Dissertation Award winner from the American Association of State Climatologists and past president of the Laura Ingalls Wilder Legacy and Research Association.

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