What kind of winter is coming to Colorado?
September 18, 2008
WESTERN COLORADO ” Ocean temperatures suggest a greater chance of average or slightly below average snowfall in western Colorado this winter, a meteorologist said.
Forecasters look to the seas to try to predict weather further out than seven to 10 days when individual storms can no longer be tracked. With winter approaching, Pacific Ocean temperatures near the equator are normal ” neither the La Nina or El Nino phenomena, which tends to go through cycles of 6 to 18 months, seem to be developing.
Joe Ramey, who works at a National Weather Service office in Grand Junction, said that while equatorial Pacific temperatures are generally an important factor in seasonal outlooks, they don’t seem to have a strong correlation for snowfall in Western Colorado. So in addition to equatorial Pacific temperatures, Ramey has been looking at “Pacific decadal oscillation” ” or ocean temperatures off the coast of Alaska ” that tend to go through 20- to 30-year cycles.
“If we combine the two maybe we can add more quality to the forecast,” Ramey said.
Ramey said he went through historic data for winters like this one ” with no La Nina or El Nino effect and colder than normal northern Pacific temperatures ” and it showed “a real trend toward near-normal precipitation across northwestern Colorado and below-normal in southern Colorado.”
He reviewed data from sites in Steamboat Springs, Winter Park, Crested Butte and Telluride, which have some of the longer and more consistent climate records.
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Forecasters do the best they can with the available science. But seasonal forecasts are more or less an educated guess. Any winter could easily not follow the trends tat winters with similar ocean conditions followed. Ramey said he wouldn’t be betting a whole lot of money on trying to predict what will happen this winter.
“By March or April I’ll have it down pat,” he said.
However, Ramey said the data for winters with similar ocean temperatures also suggests an increased chance of a high pressure ridge building and causing “kind of a mid-season melt” in January or February.
The National Oceanographic and Atmospheric Administration’s Climate Prediction Center’s seasonal outlook ” which is aimed at larger regions ” calls for a greater likelihood of above-normal temperatures this winter, Ramey said.
Even if ocean temperatures suggested better chances of more snow this winter, it would be tough to top snowfall last winter. After a dry November, Colorado saw more snow than it had in at least 10 years. Snowpack in the state was 135 percent of a 30-year average in March.
“Last year was certainly an unusual year,” Ramey said. “It was the wettest La Nina year on record in western Colorado.”