Ski Areas Indifferent to El Nino/La Nina (as of 2022)
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.v2 since 1979 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 was the 3rd highest in the past 50 years. The 2015-16 El Nino ended abruptly in JUN/JUL, falling to +0.312. The northern spring months are the historically most likely time for an El Nino or La Nina to break up, as occurred for all 5 events from 2007-2016.
There were no material El Nino or
La Nina deviations in the MEI index from 2017-2020 aside from a mild La Nina in early 2018,
so I did not update the data presented here until after the moderate La Nina of 2020-21.
That La Nina has persisted and with its highest reading of -1.9 in MAY/JUN 2022
it is a heavy favorite to last into the northern winter 2022-23 season.
The MEI index came to an end in OCT/NOV 2018, but is still the most useful for
calculating month-to-month correlations because it dates to 1950. The graph
at the top of this page is the new MEI.v2, which dates to 1979 but is updated
monthly going forward. The two MEI indicies are calculated differently but are
95% correlated. MEI.v2 is used to compare snowfall for NOV/DEC 2018 and later months.
I have correlated the
monthly MEI
table with all of the monthly
snowfall data I have collected through 2022. The list of ski areas
insensitive to El Nino/La Nina, along with their monthly and season
correlations to the MEI index (MEI.v2 since 2019) and average
snowfall during strong El Nino and La Nina months, is shown below: 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.
Area
Monthly
Seasonal
Seasons
Strong
Strong
El Nino
La Nina
Minimal
sensitivity to El Nino/La Nina
Monarch, Colo.
7.8%
106%
88%
Sugar Bowl, Calif. 7,000
5.4%
107%
104%
Snowshoe, W. V. 4,849
5.4%
87%
89%
Wolf Creek, Colo. 10,672
5.3%
100%
100%
Purgatory, Colo. 10,000
5.1%
99%
97%
Telluride, Colo. 11,171
5.0%
106%
102%
Alpine Meadows, Calif. 7,000
4.0%
11.0%
52
105%
101%
Red Mt. Pass, Colo. 11,090
4.0%
-1.8%
32
107%
107%
Arapahoe Basin, Colo. 10,820
4.0%
3.3%
35
105%
95%
Mt. Rose, Nev. 8,600
3.9%
111%
97%
Kirkwood (Carson Pass), Calif. 8,526
3.7%
11.1%
48
102%
96%
Central Sierra Snow Lab - Boreal, Cal.
7,200
3.5%
10.4%
55
106%
104%
Loveland, Colo. 11,200
3.5%
0.9%
41
105%
95%
Winter Park Base, Colo. 9,268
3.4%
0.0%
15
Red Mt. 2, B. C. 6,680
3.2%
101%
99%
Aspen Mtn, Colo. 11,190
3.2%
100%
100%
Squaw Valley, Calif. 8,000
2.8%
86%
100%
Remarkables, New Zealand 5,203
2.8%
-4.4%
Berthoud Pass, Colo. 11,315
2.7%
7.6%
48
102%
97%
Mt. Hutt, New Zealand 4,602
2.3%
1.9%
Sugarloaf, Maine 3,715
1.8%
8.2%
56
Mary Jane at Winter Park, Colo. 10,800
1.0%
2.5%
47
104%
97%
Heavenly Valley, Calif. 8,400
0.7%
7.4%
32
99%
106%
Beaver Creek, Colo. 11,200
0.5%
101%
98%
Sun Valley, Idaho 8,800
0.2%
96%
96%
Alyeska, Alaska 1,400
-0.2%
3.7%
40
115%
120%
Squaw Valley, Calif. 6,200
-0.3%
-21.2%
32
113%
102%
Gothic, Colo. 9,400
-0.6%
0.7%
48
103%
99%
Snowbird, Utah 8,100
-1.1%
1.4%
43
95%
98%
Northstar, Calif. 7,800
-1.4%
91%
102%
Alta Guard UDOT, Utah 8,680
-1.8%
-0.1%
55
97%
101%
Vail, Colo.
11,250
-2.2%
-6.3%
28
103%
101%
Sun Peaks, B. C. 6,100
-2.6%
94%
97%
Coronet Peak, New Zealand 4,032
-2.9%
Sunlight, Colo.
-3.0%
Mt. Washington, B. C. 3,926
-3.1%
Park City 2, Utah 9,280
-3.2%
1.2%
44
95%
100%
Keystone, Colo. 11,671
-4.2%
101%
101%
Snow Basin, Utah 7,710
-4.3%
5.8%
26
90%
99%
Copper Mtn, Colo. 11,000
-4.9%
100%
98%
Blackcomb, B. C. 5,002
-5.3%
-8.4%
17
Mt. Snow, Vt. 3,600
-5.6%
Brighton, Utah 8,740
-5.7%
-10.2%
18
105%
101%
Killington, Vt. 4,142
-7.0%
-14.5%
56
93%
94%
Mt. Washington, N. H. 6,263
-7.1%
-12.4%
56
93%
95%
Aspen Highlands, Colo. 11,100
-7.2%
97%
105%
Jupiter Bowl, Utah 10,000
-7.3%
0.1%
34
97%
102%
Whistler Roundhouse, B. C. 6,000
-7.6%
-9.7%
43
101%
111%
Stratton, Vt. 3,875
-7.8%
-1.5%
32
87%
89%
Big White, B. C. 6,200
-8.8%
-17.5%
37
83%
96%
Sugarbush, Vt. 3,000
-10.1%
-5.6%
35
83%
86%
Waterville Valley, N. H. 3,000
-11.3%
87%
89%
Breckenridge, Colo. 11,100
-11.9%
94%
103%
Deer Valley, Utah 8,200
-12.0%
