What is ENSO and How Will it Affect The Ski Season? - A Colorado Weather Outlook

Submitted by Caleigh Smith on Mon, 09/25/2017 - 11:27
Photo by Dave Camara courtesy of Arapahoe Basin. Photo by Dave Camara courtesy of Arapahoe Basin.

As October peeks around the proverbial corner, anticipatory skiers are starting to pore over snowfall predictions for the upcoming season. A myriad of sources presents a myriad of outlooks, ranging from dry, bleak, and stormless to a glorious powder fest across the west. Heres a digestible compilation of data from typically accurate sources to feed your pre-season snow hunger.

To provide an informational baseline, one of the most significant weather patterns that affect winter precipitation in Colorado is ENSO, short for El Nio-Southern Oscillation. ENSO is a climate pattern that affects rainfall and temperature globally, and it all starts with changes in water temperature in the tropical Pacific Ocean.

The temperature fluctuations that dictate climatic differences and Colorados ski season profitability begin in the central and eastern regions of the Pacific, hereafter referred to as SST, or sea surface temperature. When SST is below average and there is high air pressure in the eastern Pacific combined with low air pressure in the western Pacific, the cool phase of ENSO is initiated. This is called La Nia.

El Nio is the opposite, warm phase of ENSO. During El Nio, SST is warmer on average in the central and east-central Pacific between the International Date Line and 12o W combined with high air pressure in the western and low air pressure in the eastern Pacific.

The SST in the tropical Pacific has been dropping throughout this summer with a large welling of cooler water below the surface. A jet stream off the Pacific Ocean flowing over the northwest US will push wetter conditions over southern Montana, Wyoming, central and northern Colorado, and east over much of the Midwest. According to NOAA, the National Oceanic and Atmospheric Administration, there is a 55-60% chance of La Nia occurring this fall and winter.

So, what does that mean for Colorado Ski Country?

Colorado, Utah, Wyoming, Montana, and Idaho are expected to enjoy normal to above normal snowfall this winter. For some close-to-home relatability, Steamboat and Loveland are expected to be at 115% of normal snowfall with Aspen and Wolf Creek weighing in at a comfortable 100%.

According to the Farmers Almanac, the winter will not be as harsh as usual with slightly warmer temperatures and the snowiest times of the season being mid-to-late-November, mid-to-late-December, and early-to-mid-March. As is common for Colorado, we should be seeing some precipitation pushed in from the Pacific jet stream and bouts of cold air from Canada.

Weather prediction has mixed reviews and mixed success, and I am no meteorologist, but if all contributing data is correct, we at CSCUSA might be enjoying some deep and luscious powder this season. Bring it on, La Nia, we welcome you!

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