A good winter could be in store for southern Colorado ski resorts that endured drought last season, thanks to a reappearance of the climate phenomenon known as El Niño in the Pacific Ocean.
Weather forecasters and climatologists say it’s too soon to say with reliability what kind of snowfall patterns are likely for Colorado, but a report issued this month by the National Oceanic and Atmospheric Administration’s Climate Prediction Center said a weak El Niño is forming and is expected to build through the winter.
The building El Niño — the weather pattern that occurs when surface temperatures in the tropical Pacific are above average — may be responsible for a series of tropical storms in the eastern Pacific in recent weeks.
El Niño cycles tend to favor storm tracks from the Pacific that move across the southern U.S., and in some years that bodes well for southern Colorado resorts. Last winter featured a mild La Niña — the opposite of El Niño — which is related to below-normal Pacific surface temperatures. Northern Colorado resorts had near-normal snowfall while southern Colorado suffered.
NOAA said there is a slight positive probability of above-normal precipitation in southern Colorado from November to January and an equal probability of normal precipitation in northern Colorado.
“That summarizes pretty well what we’re looking at,” said Russ Schumacher, Colorado state climatologist for the Department of Atmospheric Science at Colorado State University. “We’re not quite in El Niño yet, but it looks very, very likely that’s what we’re going to see this winter.”
Forecasting El Niño’s effects is a tricky proposition, though.
“The trouble with El Niño is that Colorado sits right in between the areas where it has its strongest effects,” Schumacher said. “It tends to be wet in El Niño years across Texas and down along the Gulf Coast, then dry and warm to the north of us in Montana, Wyoming.”
Southern Colorado often is right on the edge of that prevailing storm track, and that complicates predictions even more.
“It depends on where that southern branch of the jet stream sets up,” said Bernie Meier, a forecaster for the National Weather Service in Boulder. “If it sets up to the south, we are kind of left high and dry. Sometimes it clips Colorado, and central and southern Colorado generally sees the effects from that.”
The outlook for the northern mountains is even more difficult to forecast.
“We’ve had weak El Niño years that have been very snowy in the northern mountains and weak El Niño years that have been very not snowy in the northern mountains,” Schumacher said. “It’s really hard to say anything with a whole lot of certainty.”
Colorado is off to a good start for mountain snowfall, though, and more is on the way.
“We’re doing actually pretty well in the mountains for this time of year,” Meier said. “We’re sitting at almost twice what we usually have this time of year. Probably 5 percent of normal has fallen already, and we don’t look to lose that in the next few days. Next week looks cool, with a couple systems, so it looks like through the first week of November we’re going to have a good start to the snow season for all the mountains of Colorado.”
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