Winter forecast, part I: the woolley bear prediction

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 on either end of the caterpillar is thick, the winter will be a mild one. A narrow brown stripe portends a long, cold winter. Some traditional forecasters say that the 13 segments on the caterpillar's body correspond to the 13 weeks of winter.

The Hagerstown, Maryland woolley bear forecast
The Hagerstown, Maryland Town and Country Almanack has been publishing weather forecasts and weather lore for 211 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. The results of this year's contest, which ended October 31: "From the small number of woolly bears, the consensus is that the winter will be very mild. The woolly bears predicted this by their three (3) bands of which the front band (representing the first half of winter and black in color) was shorter in length and normal. The back band (representing the second half of winter) was very small, thus indicating the mild winter prediction. As a result of those markings, which were similar in all woolly bears, the sponsors were able to make the predictions."

Oil Valley Vick
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. In Oil City, Pennsylvania, just 150 miles northwest of Hagerstown, organizers of the Pumkin Bumkin Festival have located the lair of "Oil Valley Vick", a woolly bear caterpillar of unknown forecasting ability, but great potential. In his inaugural forecast on October 23 this year, Oil Valley Vick wowed the crowd at the Pumkin Bumkin Festival when he crawled out of his log. The black stripes covering fully 2/3 of Oil Valley Vick's body left no doubt that he expected a cold, severe winter for northwestern Pennsylvania.


Figure 1. Kelly the woolly bear caterpillar with her owner, six-year-old Kurstin Hartsell of Ansonville, NC. Image credit: Jim Morton, Avery County Chamber of Commerce.

The Banner Elk, North Carolina Woolly Bear forecast
In Banner Elk, NC it's the fastest woolly bear caterpillar which is judged to be the best forecaster. After successfully out-sprinting hundreds of other woolly bears, this year's winner of the 31st Annual Woolly Worm Festival race was Kelly the Woolly Worm, raced by six-year-old Kurstin Hartsell of Ansonville, NC. Kelly the Woolly Worm's official forecast for the winter of 2008-2009 calls for the first four weeks to be cold and snowy, followed by three weeks of seasonably cold weather, followed by six weeks of snowy and cold weather (severely cold in week 11, March 1-7). A study of the predictions of the Banner Elk woolly bears between 1978 and 2000 revealed that "woolly worm winter predictions were exactly on target eight times out of 23, or 34.8%. Woolly worm predictions were close (4.0-4.9) another five times (21.7%). Woolly worm predictions were right in some areas, wrong in others (3.0-3.9) six times (26.1%). Woolly worm predictions were wrong more than they were right (2.0-2.9) four times (17.4%). Put another way, the woolly worms were close or completely right 57% of the time, and more than half right 82.6% of the time".

Other studies of woolly bear forecast accuracy
Several scientific studies have been done on woolly bear caterpillar forecasts, including one by the American Museum of Natural History. None of these studies has shown any correlation between woolly bear markings and the severity of the upcoming winter. According to the Old Farmer's Almanac, Dr. Charles Curran, curator of insects at the American Museum of Natural History in New York City, studied woolly bear markings between 1948-1956 in Bear Mountain State Park, 40 miles north of New York City. He found some preliminary results that seemed to indicate that the thickness of the bands might indicate the severity of the upcoming winter. However, 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, according to science writer Ned Rozell.

So, two out of three woolley bear forecasts point to a colder than average winter for the Appalachian region of the U.S. In upcoming blog posts, I'll analyze what NOAA's computer models and the Old Farmer's Almanac have to say about the upcoming winter.

Portlight making keynote presentation at charity funding conference today
The Portlight.org charity is making the keynote presenation at a funding conference hosted by a coalition of state and federal agencies which work in the area of post-disaster relief involving people with disabilities. The presentation is this morning, November 20, at 9:15 am EST. You can follow the proceedings via the portlight webcam at stormjunkie.com. At the conference, they plan to discuss the Hurricane Ike relief efforts made possible by the Weather Underground community. Thanks for everyone's support for making all this possible!

Jeff Masters