Factors similar to record-setting ’83/’84 season
Similar atmospheric and oceanic factors as the record-setting winter of 1983-’84 are in place going into this ski season, AspenWeather.net’s meteorologist said during Thursday night’s winter snowfall forecast, leading him to predict 10 to 20 percent above average seasonal totals.
Corey Gates, who along with Ryan Boudreau has put out daily forecasts on the subscription-based website for five years, said this winter’s weather pattern will be marked by a weak La Nina — meaning cold water near the equator in the Pacific Ocean — and a warm Pacific Decadal Oscillation (PDO) pattern, meaning warmer temperatures in the North Pacific.
“The oceans drive everything,” said Gates, who worked as a forecaster for 20 years with the National Oceanic and Atmospheric Administration in North Carolina before coming to the valley.
A weak La Nina and a warm PDO have been in place in just three other winters since 1950 — including ’83/’84, when it snowed 278 inches in town — and in-town snowfall averaged a well-above-normal 223 inches for October through May in those years, Gates said. In the 11 weak La Nina winters since 1950, average snowfall was 168 inches in town, which is about 10 percent above normal.
Gates’ method for making winter-long predictions involves looking at averages in past years with similar La Nina or El Nino patterns, and looking at current atmospheric conditions and models.
“The weather repeats itself,” he said during the event that packed the lounge at the Limelight hotel. “It just does. There is no doubt.”
The key, he said, is a ridge of high pressure at the 140-west longitude line, which intersects Alaska. When that happens, snowfall is a near guarantee in Aspen, because the downsloping trough comes right over the Colorado Rockies.
Gates is calling for 368 inches at Snowmass in the months between October and May, 353 inches at Aspen Highlands, 337 inches at Aspen Mountain and 184 inches in town. Those totals are all higher than last year’s predictions and verified results.
Going month by month, Gates said it will snow in November, which carries certain advantages — it’s good for the tourism industry when early season snow gets written up in the media, and the cold temperatures help the Aspen Skiing Co. with its snowmaking operations.
December and January are “dangerous” — in a good way — Gates said, referencing a projected ridge at 140-west, and the emphasis on the northern jet stream that comes with the weak La Nina.
“The storm track will come plowing down through the northwest, just like it did in ’83/’84,” he said.
March should also be good, he said, before a mid- to late-spring dry out, which he warned could pose wildfire dangers.
January will be the snowiest month this winter, which will see average to slightly above normal temperatures, Gates predicted.
He added that his confidence level in his winter forecast is a nine, presumably out of 10. He also said he’s erring on the side of caution, so it could wind up snowing more.
Gates nailed it with his predictions last year, said Boudreau, his partner in the website. At the winter forecast event last September, for the winter season running from October through early May, Gates predicted 358 inches at Snowmass, 333 inches at Aspen Highlands, 329 inches at Aspen Mountain and 171 inches in town. He correctly forecasted that the early and late winter months would see ample precipitation, with a dry period sandwiched in the middle.
Verified totals last year were mostly slightly ahead of his estimates for above average snow: 359 inches at Snowmass, 345 inches at Highlands, 323 inches on Ajax and 171 inches in town.
“This guy is a special talent,” Boudreau said.