Ski Areas Indifferent to El Nino/La Nina (as of 2016)
On my El Nino page I introduced the Multivariate ENSO Index , which is considered by many meteorologists to be the best overall measure of the strength of El Nino/La Nina. The graph of MEI since 1950 is repeated 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, 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 in the past 50 years) through FEB/MAR, then dissipated over the next 3 months to a neutral value of +0.050 as of MAY/JUN 2008. Similarly the El Nino of 2009-10 was strong through FEB/MAR (the 7th highest El Nino in the past 50 years), but MEI turned negative by MAY/JUN. By AUG/SEP 2010 MEI registered -1.99, the strongest La Nina reading since 1955. The La Nina of 2010-11 remained strong through MAR/APR (the 2nd highest La Nina in the past 50 years) before weakening abruptly in APR/MAY 2011. La Nina strengthened to a moderate level for fall 2011 and gradually weakened starting JAN/FEB 2012. The MEI Index did not have a sustained significant El Nino or La Nina stretch for the next 3 ski seasons. The 2015-16 El Nino exceeded +2.0 for all but one month from MAY/JUN 2015 through MAR/APR 2016 and is the 3rd highest in the past 50 years. The northern spring months are the historically most likely time for an El Nino or La Nina to break up, as occurred for all 4 events from 2007-2012. The 2015-16 El Nino showed its first major sign of weakening in MAY/JUN, falling to +1.029.
I have correlated the monthly MEI table with all of the monthly snowfall data I have collected through 2007. The list of ski areas insensitive to El Nino/La Nina, along with their monthly and season correlations to the MEI index and average snowfall during strong El Nino and La Nina months, is shown below:
|El Nino||La Nina|
|Minimal sensitivity to El Nino/La Nina|
|Heavenly Valley, Calif. 10,000||6.5%|
|Wolf Creek, Colo. 10,652||3.7%||100%||96%|
|Snowshoe, W. V. 4,849||3.6%||92%||94%|
|Winter Park Base, Colo. 9,266||3.4%||0.0%||15|
|Alpine Meadows, Calif. 7,000||3.1%||6.9%||46||108%||106%|
|Sugar Bowl, Calif. 7,000||2.9%||106%||114%|
|Remarkables, New Zealand 5,203||2.8%||-4.4%|
|Central Sierra Snow Lab - Boreal, Cal. 7,200||2.6%||6.4%||50||109%||107%|
|Mt. Hutt, New Zealand 4,602||2.3%||1.9%|
|Telluride, Colo. 11,170||1.8%||106%||107%|
|Kirkwood (Carson Pass), Calif. 8,526||1.7%||6.0%||42||103%||103%|
|Heavenly Valley, Calif. 8,400||1.7%||8.4%||31||103%||109%|
|Red Mt. 2, B. C. 6,660||1.5%||101%||102%|
|Mt. Rose, Nev. 8,600||1.4%||104%||104%|
|Purgatory, Colo. 10,000||1.3%||98%||98%|
|Red Mt. Pass, Colo. 11,090||0.4%||-16.5%||26||105%||115%|
|Arapahoe Basin, Colo. 10,820||-0.4%||-5.8%||29||102%||102%|
|Squaw Valley, Calif. 8,000||-0.7%||91%||111%|
|Aspen Mtn, Colo. 11,190||-1.0%||100%||105%|
|Alyeska, Alaska 1,400||-1.1%||2.3%||34||112%||117%|
|Loveland, Colo. 11,200||-1.1%||-9.4%||35||103%||100%|
|Mary Jane at Winter Park, Colo. 10,800||-1.2%||-0.8%||41||102%||98%|
|Sun Valley, Idaho 8,800||-1.4%||99%||105%|
|Berthoud Pass, Colo. 11,315||-2.0%||-3.7%||42||101%||103%|
|Squaw Valley, Calif. 6,200||-2.9%||-36.0%||26||110%||107%|
|Coronet Peak, New Zealand 4,032||-2.9%|
|Mt. Washington, B. C. 3,926||-3.1%|
|Waterville Valley, N. H. 3,000||-3.4%||92%||94%|
|Sugarloaf, Maine 3,705||-4.9%||1.4%||50|
|Beaver Creek, Colo. 11,200||-5.1%||98%||100%|
|Blackcomb, B. C. 5,002||-5.3%||-8.4%||17|
|Sun Peaks, B. C. 6,100||-5.5%||92%||105%|
|Mt. Snow, Vt. 3,600||-5.6%|
|Northstar, Calif. 7,800||-5.9%||89%||112%|
|Gothic, Colo. 9,400||-6.1%||-11.6%||42||99%||106%|
|Alta, Utah 8,660||-6.4%||-10.6%||49||96%||106%|
|Brighton, Utah 8,740||-6.6%||-9.4%||38||96%||108%|
|Whistler Roundhouse, B. C. 6,000||-6.7%||-9.0%||37||105%||118%|
|Keystone, Colo. 11,651||-6.9%||97%||108%|
|Park City 2, Utah 9,280||-7.9%||-9.3%||38||94%||106%|
|Killington, Vt. 4,142||-8.0%||-17.7%||50||91%||95%|
|Vail, Colo. 11,250||-8.1%||-26.9%||22||100%||105%|
|Big White, B. C. 6,200||-8.2%||-17.6%||31||85%||99%|
|Snow Basin, Utah 7,700||-8.6%||91%||106%|
|Mt. Washington, N. H. 6,263||-9.2%||-17.2%||50||93%||98%|
|Copper Mtn, Colo. 11,000||-9.9%||96%||101%|
|Snowbird, Utah 8,100||-11.7%||-21.6%||43||91%||110%|
|Breckenridge, Colo. 11,100||-11.9%||93%||104%|
|Deer Valley, Utah 8,200||-12.0%|
|Stratton, Vt. 3,875||-12.4%||-14.7%||27|
|Aspen Highlands, Colo. 11,100||-13.7%||97%|
|Whiteface (Lake Placid), N. Y. 3,660||-13.9%||92%||94%|
Note that there are 54 areas listed here, vs. 11 that are favored by El Nino and 39 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. A couple of Utah Wasatch locations were moved to the mildly La Nina favored group due to excess snowfall in strong La Nina vs. strong El Nino months. Overall Wasatch snowfall during strong La Nina months exceeds snowfall during strong El Nino months by 10-15%, 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 20% excess snowfall in the strong La Nina months. At nearby Gothic and 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, illustrating that Tahoe area 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.
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 record El Nino of 1983 was its second highest snow season. Grand Targhee and Big Sky have relatively modest correlations, but both are now classified as mildly favored by La Nina due to strong La Nina month snowfall exceeding snowfall during strong El Nino months by 18-19%. 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. The vertical axis is percent deviation from normal snowfall. The blue line is the sum of MEI indicies from OCT/NOV to APR/MAY, 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 54 areas listed in the Minimal Sensitivity list above.
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