Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 1:52 PM GMT on November 08, 2005
And now for something completely different: the woolly bear caterpillar forecast for the coming winter. After months of focusing on the death and destruction wrought by the fury of nature's hurricanes, and now tornadoes, it's time to take a break. The tropics remain quiet again today, allowing us to indulge. The political discussions can wait until another day.
According to legend, the severity of the upcoming winter can be judged by examining the pattern of brown and black stripes on woolly bear caterpillars--the larvae of Isabella tiger moths. If the brown stripe between the two black stripes is thick, the winter will be a mild one. A narrow brown stripe portends a long, cold winter.
The Hagerstown, Maryland Town and Country Almanack has been publishing weather forecasts and weather lore for 209 years. The Almanack sponsors an annual woolly bear caterpillar event, where local school children in Hagerstown collect woolly bears. A panel of judges examines the collected specimens and issues a woolly bear forecast for the upcoming winter. Gerald W. Spessard, the Town and Country Almanack's business manager and one of this year's two judges, observed that the middle brown stripes on the 20 caterpillars collected this year were thicker than usual. "There's not a whole lot of black at either end, so we both agree this should be a fairly mild winter," Spessard said, according to an AP press release.
Naturally, this forecast only applies to the Hagerstown, Maryland area, so other locales will need to do their own woolly bear work to gauge the local winter forecast. The Hagerstown critters have had mixed success the past three years with their forecasts--they've been correct about half the time. This is only slightly worse than the official NOAA long range forecasts.
Several scientific studies have been done on woolly bear caterpillar forecasts, including one by the American Museum of Natural History. None of these studies have shown any correlation between woolly bear markings and the severity of the upcoming winter. According to Ned Rozell, science writer at the University of Alaska's Geophysical Institute, Biologist Dr. Charles Curran began studying woolly bear markings and the severity of winters in 1948. For the first three years, the caterpillars had wide brown bands, correctly forecasting three consecutive mild winters. The caterpillars failed the next year, and Dr. Curran gave up the study in 1955 after finding two groups of caterpillars living near each other that had vastly different predictions for the upcoming winter.
So, you're probably better off using the official NOAA long-range forecast for the upcoming winter--although not by much. I'll discuss the official NOAA forecast for the upcoming winter tomorrow, and talk about how well they've done in past years.
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Light Freezing Rain