Ski Areas Indifferent to El Nino/La Nina (as of 2023)

On my El Nino page I introduced the  Multivariate ENSO Index and the Oceanic Nino Index , which are overall measures of the strength of El Nino/La Nina.  The more widely used ONI since 1990 is graphed here for convenience.

When I first wrote this article on 11/21/07 the last posted value of MEI was -1.117 for SEP/OCT 2007 (also -1.1 for ASO ONI), and I expressed strong confidence that the observed La Nina condition would be in effect through the end of 2007, and some confidence that it would persist for the entire 2007-08 ski season.  It turned out that La Nina remained strong (2007-08 was 5th highest La Nina by MEI and 3rd highest by ONI in the past 50 years) through FEB/MAR, then dissipated to near neutral by MAY/JUN for MEI and a couple months later for ONI.

Similarly the El Nino of 2009-10 was strong through FEB/MAR (the 7th highest El Nino in the past 50 years by both indicies), but both turned negative by June. By AUG/SEP 2010 MEI registered -1.88, the strongest La Nina reading since 1974, and ONI reached -1.6 in October. The La Nina of 2010-11 remained strong through April (the 3rd highest by MEI and 6th by ONI in the past 50 years) before weakening in late spring. La Nina strengthened to a moderate level by fall 2011 and gradually weakened the following spring. The MEI Index did not have a sustained significant El Nino or La Nina stretch for the next 3 ski seasons. From late spring 2015 to early spring 2016 El Nino exceeded +2.0 for 9 months by MEI and 6 months by ONI and was the highest overall by ONI and 3rd highest by MEI in the past 50 years. The 2015-16 El Nino ended abruptly in June 2016. The northern spring months are the historically most likely time for an El Nino or La Nina to break up, as occurred for all 6 events from 2007-2023.

There were no material El Nino or La Nina deviations in the MEI or ONI indices from 2017-2020 aside from a mild La Nina in early 2018 and a borderline El Nino in early 2019, so I did not update the data presented here until after the moderate La Nina of 2020-21. That La Nina persisted for 3 seasons into early 2023 but the two indices have diverged often since summer 2002 when La Nina remained consistent by ONI while strengthening by MEI. The La Nina dissipated by early spring for both but as of October 2023 has swung to moderate El Nino +1.5 by ONI but only weak El Nino +0.4 by MEI. The 1.1 divergence is very rare, only 2% of months since 1950.

In recent years most meteorologists are using the ONI, so I'm doing that too as of 2023. Since 1950 monthly ONI is 88% correlated to monthly MEI and ski season values are 94% correlated. The relationship of ski area snowfall to El Nino/La Nina is essentially the same for both MEI and ONI, The tables of ski areas insensitive to El Nino/La Nina below are calculated using ONI, and all of these ski areas have the same classification using MEI.

I have correlated the Monthly ONI Table with all of the monthly snowfall data I have collected through 2023. The list of ski areas insensitive to El Nino/La Nina, along with their monthly and season correlations to the ONI index and average snowfall during strong El Nino and La Nina months, is shown below:

Area (ONI) Monthly Seasonal Seasons Strong Strong
        El Nino La Nina
Minimal sensitivity to El Nino/La Nina          
 Monarch, Colo.    4.3% 22.6%            20 98% 94%
 Sugar Bowl, Calif.   7,000     2.0%     111% 102%
 Snowshoe, W. V. 4,849 5.3%     84% 96%
 Wolf Creek, Colo.   10,672 2.7% 34.6%            22 100% 97%
 Purgatory, Colo.   10,000  0.4%     96% 96%
 Telluride, Colo.   11,171 1.9%     103% 102%
 Alpine Meadows, Calif.   7,000   2.7% 7.1%            53 108% 101%
 Red Mt. Pass, Colo.   11,090 3.5% 7.7%            33 103% 102%
 Arapahoe Basin, Colo.   10,820 -2.8% -0.5%            36 98% 104%
 Mt. Rose, Nev.   8,600 1.1% 5.9%   110% 102%
 Kirkwood (Carson Pass), Calif.  8,526 0.0% 4.5%            49 103% 99%
 Central Sierra Snow Lab - Boreal, Cal. 7,200  2.9% 9.7%            56 110% 101%
 Loveland, Colo.   11,200   -3.0% -3.2%            42 97% 102%
 Winter Park Base, Colo.   9,268   -6.4% -8.7%            15    
 Red Mt. 2, B. C.   6,680 -0.6%     100% 102%
 Aspen Mtn, Colo.   11,190 -3.7%     95% 100%
 Palisades Tahoe, Calif.   8,000      2.8%     97% 98%
 Remarkables, New Zealand  5,203 3.8% 7.1%      
 Berthoud Pass, Colo.   11,315  -5.2% -2.7%            49 96% 103%
 Mt. Hutt, New Zealand   4,602   5.0% 3.1%      
 Sugarloaf, Maine 3,715 1.6% 9.3%            57    
 Mary Jane at Winter Park, Colo.   10,800      -4.1% -4.0%            48 96% 104%
 Heavenly Valley, Calif.   8,400    -0.8% 5.6%            32 101% 100%
 Beaver Creek, Colo.   11,200 -4.8%     93% 103%
 Sun Valley, Idaho   8,800  -0.8%     102% 98%
 Alyeska, Alaska   1,400   0.3% -3.2%            41 107% 101%
 Palisades Tahoe, Calif.   6,200      -0.6% -19.6%            33 122% 102%
 Gothic, Colo. 9,400   -6.0% -5.8%            49 92% 103%
 Snowbird, Utah   8,100   -6.1% -2.9%            44 93% 101%
 Northstar, Calif.   7,800 -2.2%     100% 104%
 Alta Guard UDOT, Utah   8,680 -6.1% -5.4%            56 92% 101%
 Vail, Colo.   11,250    -6.9% -6.8%            29 96% 104%
 Sun Peaks, B. C.  6,100 -4.4%     92% 95%
 Coronet Peak, New Zealand   4,032   -4.0%        
 Sunlight, Colo. -11.0%        
 Mt. Washington, B. C.   3,926   2.2%        
 Park City 2, Utah   9,280  -7.7% -5.5%            45 91% 104%
 Keystone, Colo.   11,671 -4.6% 7.4%            24 94% 100%
 Snow Basin, Utah   7,710  -7.6% 3.6%            27 93% 104%
 Copper Mtn, Colo.   11,000   -10.3% -23.5%            26 93% 103%
 Blackcomb, B. C.   5,002       1.0% -3.8%            17    
 Mt. Snow, Vt.   3,600 -5.9%        
 Brundage, Idaho   6,000    -25.7%            35    
 Brighton, Utah   9,502  -7.3% -9.0%            19 96% 101%
 Killington, Vt.  4,142 -3.5% -10.7%            57 99% 98%
 Mt. Washington, N. H.  6,263 -1.4% -3.6%            57 105% 100%
 Aspen Highlands, Colo.   11,100  -10.3%     96% 108%
 Jupiter Bowl, Utah   10,000 -9.8% -4.7%            35 95% 108%
 Whistler Roundhouse, B. C.   6,000       -3.5% -6.1%            44 102% 106%
 Stratton, Vt.   3,875 -7.7% -9.1%            33 84% 96%
 Big White, B. C.  6,200 -7.3% -17.5%            38 86% 93%
 Sugarbush, Vt.   3,000 -8.5% -11.9%            36 81% 90%
 Waterville Valley, N. H. 3,000  -10.4%     84% 96%
 Breckenridge, Colo.   11,100  -15.8% -13.6%            30 90% 115%
 Deer Valley, Utah   8,200 -16.9%        

Note that there are 57 areas listed here, vs. 9 that are favored by El Nino and 36 favored by La Nina.  In particular, with the exceptions of Brian Head and Steamboat El Nino/La Nina have minimal predictive value for Utah and Colorado ski areas. Overall Utah asatch snowfall during strong La Nina months exceeds snowfall during strong El Nino months by arpund 10%, which is a borderline call given only 25-45 months in each strong category. Data volatility is even more evident for Crested Butte and Snowmass being moved to mild La Nina due to 18% excess snowfall in the strong La Nina months. At nearby Aspen Mt. the La Nina over El Nino snowfall excess is an insignificant 5%.

In the El Nino favored page I analyzed the data from Donner Pass near Lake Tahoe and Mammoth, illustrating that Sierra snowfall is not as sensitive to El Nino as most people think.  Note here that for all the Tahoe areas both strong El Nino and strong La Nina months average close to each other and to 100% of normal. The most southwestern locations in Colorado  like Purgatory, Telluride and Red Mt. Pass (also presumed by many to be favored by El Nino) have even smaller correlations than the Lake Tahoe areas along with similar averages in the strong El Nino and La Nina months. Most of these southwestern locations had record snowfall during the strong La Nina of 2007-08. Many Sierra areas had record snowfalls during the La Ninas of 2010-11 and 2022-23.

Most Northern Rockies areas are favored by La Nina, but there are a few microclimates that are less sensitive. Sun Valley and Sun Peaks have fairly dry climates that are blocked out of some prevailing weather patterns. It is well known that Sun Valley gets its biggest dumps from the south, and the strong El Nino of 1983 was its second highest snow season. Red Mt. is perhaps the biggest surprise, as it shows little sensitivity by either correlation or strong El Nina/La Nina months, yet it is surrounded by areas that all favor La Nina quite strongly.

In the La Nina favored page I noted that the Whistler alpine and New Zealand are not as sensitive to La Nina as many people assume.

And finally, the Northeast is minimally affected by El Nino/La Nina, with a few scattered anomalies favored by La Nina, of which Cannon Mt. is the strongest.

The contrasting 2010-11 and 2011-12 La Nina seasons drive home the irrelevance of El Nino/La Nina to these regions. Tahoe, Utah and I-70 Colorado all had huge seasons in 2010-11 and severe drought seasons in 2011-12. I-70 Colorado in particular had some record high snowfalls in 2010-11 and some record lows in 2011-12.

I have constructed graphs to illustrate the variability of the snowfall correlations to El Nino/La Nina.  The one below is for selected areas with minimal sensitivity to El Nino/La Nina.

The horizontal axis lists all the past ski seasons since 1966-67 in order of strong El Nino at left to strong La Nina at right according to ONI.  The vertical axis is percent deviation from normal snowfall. The blue line is the sum of ONI indices from OND to MAM, scaled to fit the graph.

The areas above were selected for complete data since 1966-67.  Berthoud Pass (yellow line) is a good representative for the numerous areas along the I-70 corridor in Colorado, ranging west to Aspen.  Killington (orange) and Mt. Washington (light blue) represent a couple of climate zones in the Northeast.

If you look at the 8 strongest El Nino and La Nina seasons, Alta (purple), Berthoud, Mt. Washington and Killington all have at least 2 above average seasons and 2 below average seasons in each group.

Overall the graph shows why El Nino and La Nina do not predict snowfall well for the 57 areas listed in the Minimal Sensitivity list above.

 

Ski Areas Favored by El Nino

Ski Areas Favored by La Nina

 

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