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Another warm winter? Forecasters just shrug

Published: Friday, Oct. 12, 2012 9:29 a.m. CDT

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(MCT) — After a mild winter and a scorching, record-setting summer, a question looms: What does winter have in store?

The short answer: Hard to say.

With a witches' brew of variables still unknown, long-range weather forecasts that carry into the deep-freeze months can be a lot like reading tea leaves, experts say.

One thing they do agree on — it's about time for the Chicago area to taste a "hard frost," where the temperature drops to 28 degrees or lower. Temperatures fell below the freezing mark in a handful of suburbs last week, but not in Chicago.

"We are in the frost window," said climatologist James Angel of the Illinois State Water Survey, adding that Chicagoans should expect to wake up one morning after a cold, clear night to frost coated windows and crunchy grass.

"It's coming."

Determining what else may be coming and when it will arrive as trees begin to lose their leaves is more difficult to assess, climatologists say. Still, everybody wants to know what winter has in store.

The stakes are significant. Farmers need to know what to expect. Retailers will consult long-range forecasts before stocking store shelves with shovels and salt, and utility companies will balance energy supplies with projected demand depending how cold the winter is expected to be.

Last winter was among the warmest on record in the Chicago area and in the rest of the country since record keeping began in 1895, according to the National Oceanic and Atmospheric Administration.

The average temperature last winter was 32.8 degrees, 6.4 degrees warmer than the climatological average. Chicago residents used to bundling up through Easter basked in the 70-and 80-degree highs in March, wore sandals on St. Patrick's Day and took kids to the local beaches over spring break.

"We just totally shattered the record temperature for March," said Kevin Birk, a meteorologist for the National Weather Service.

But whether this winter will be a repeat or more characteristically cold is hard to know because the scientific data forecasters use to analyze temperatures and other atmospheric conditions focus mainly just a few days ahead.

Determining a long-range forecast requires the ability to predict how larger climate-scale issues will unfold, such as an El Nino weather pattern that affects ocean temperatures interacting with the atmosphere

Pressure anomalies across the North Atlantic and Arctic also factor in, Birk said.

"There's a lot of things we really don't understand about all the mechanisms and how they work against each other," Birk said. "The way the science is today, we just don't know enough to give a skillful answer."

Still, certain weather prognosticators are willing to stick their necks out a little farther. Sometimes they get it right; other times they miss their mark completely.

AccuWeather.com issued a long-range forecast for the 2011-12 winter with the caveat: "People in Chicago are going to want to move after this winter," according to a news release last fall.

This year, AccuWeather is forecasting a mild winter, with a slight chance of above-normal temperatures.

The Farmers' Almanac predicts a return of "real winter" to parts of the U.S., including the Great Lakes region, and snowstorms between Feb. 12 and 15.

According to the almanac's long-range forecast, winter temperatures in the Chicago area will be slightly higher than average.

Snowfall and precipitation will be less overall, with mid-November, early January and early March the whitest, the almanac says.

"We go out on a limb to say what's going to happen six or 12 months down the road," said Sandi Duncan, managing editor of the almanac.

It's much more than most climatologists are prepared to say about the approaching season at this early date.

Tom Skilling, chief meteorologist for WGN-Ch. 9, said that up until a few weeks ago, he and other forecasters thought a mild winter might lie ahead because there appeared to be a strong El Nino weather pattern steering mild air over the continent.

But today, that pattern looks weak, if not nonexistent. And forecasters have also noticed a dome of warm air in the high latitudes above Greenland, which could signal a more traditional Chicago winter with cold outbreaks and snow, said Skilling, whose forecasts appear daily in the Tribune.

But it's never that simple, Skilling added.

Statistically, warm winters are followed by warm winters two out of three times, he said.

"We don't have all the mysteries of seasonal forecasting worked out yet," Skilling said.

It certainly felt like winter was in the air last weekend, when temperatures dipped below freezing in some areas surrounding the city.

Angel, the Illinois State Water Survey climatologist, said the first hard frost of the year usually hits Chicago by Oct. 15, about a week later than most of the other parts of northern Illinois because densely populated, urban areas stay warmer longer. The warmer temperatures of Lake Michigan also have an insulating effect.

According to data maintained by the water survey, the date of the first hard frost — tracked by temperature rather than observation of the cold crystals glimmering on blades of grass — varies considerably.

Oct. 27 is the average date for the first hard frost, but it has happened as early as Oct. 2 and as late as Dec. 3, according to the water survey.

"If you just bought some awesome mums and you want them to last, if they are portable, put them in your garage," warned Matthew Barrett, who oversees all of the flora grown at the Garfield Park Conservatory.

Barrett said he's watching the forecasts religiously to protect their collection.

"Two or three days before the frost warning, and we have already got the wheels in motion," he said.

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