The early season storms that have dropped record and near-record snows in the local mountains could be consistent with a developing and strengthening El Niño weather pattern, according to Boulder-based climate researcher Klaus Wolter.
Although his official winter forecast isn't due until next month, Wolter offered a seasonal outlook for more than 100 snow-safety experts gathered for an avalanche workshop at Copper earlier this week, calling for a wetter-than-average late winter and spring.
Big storms rolling in from Southern California can be traced to El Niño, part of a periodic shift in ocean surface temperatures in the Eastern Pacific. Where exactly those storms track once they reach the central and southern Rockies is still hard to project. In some years, El Niño has a potent effect in the Southwest, including Colorado's San Juan mountains.
"It's not a straightforward thing in the fall," Wolter said.
"Typically, you don't get those classic El Niño storms that barrel in from Southern California. But rather you get these storms that interact with a lot of subtropical moisture that comes in, from Eastern Pacific storms ... which tend to get enhanced in El Niño conditions. We've already had our share of that this year," he said.
"I wasn't snowed in yesterday, but it was close," Wolter continued. At his mountain home west of Boulder, Wolter said the wettest Octobers that he has recorded have all been during El Niño episodes - in 1997, 2002 and this year. Wolter has been tracking weather at that location for 17 years. In general, October is the driest month of the year in Colorado.
Local National Weather Service observer Rick Bly said he's found a statistical correlation between October precipitation and winter trends, based on records going back more than 100 years. When October brings above-average moisture, there's a 70 percent chance the rest of the winter will also be wetter than average, Bly said.