El Nino: Was 1997-98 a Replay of 1982-83?

I have received numerous e-mails inquiring about the impact of El Nino upon the 1997-98 ski season. Cold currents normally flow from the poles toward the equator along the west coasts of both North and South America, with an equatorial current flowing east to west across the Pacific. El Nino is a reversal of this normal pattern, resulting in warmer than normal water temperatures in the eastern Pacific. Here in Southern California, ocean temperatures have been consistently about 5 degrees F warmer than normal since last summer.

El Nino has its most direct effect upon areas close to the equatorial Pacific. South America had a huge 1997 ski season, with big dumps beginning in May and a 10 foot base reported in most Chilean resorts by mid-July. Conversely, Australia and New Zealand had essentially no snow before July 1, although snowfall since late July was near normal. The previous major El Nino of 1982 resulted in Australia's driest winter of the last 40 years.

The table below shows snowfall at North American areas during the previous major El Nino season of 1982-83. The most conspicuous results are the extremely high totals from California, which were hyped by our local weather reporters. El Nino raises temperatures as well as precipitation, so note that there was great divergence in snowfall between the higher and lower altitude areas of the Pacific Northwest. The Northeast had a poor season, and results from continental western ski regions did not seem unusual. Some researchers believe that a strong El Nino may influence the North Pacific jet stream and storm track to take a more southerly course than normal. However, the 1978-79 and 1992-93 seasons had consistent southern storm tracks and I never recall hearing El Nino mentioned as the reason. Another theory is that the jet stream is more likely to split, bringing high precipitation to Alaska and the Southwest and leaving a drought "hole" in between. There were a couple of split jet episodes in late fall and early spring of 1997-98, but this pattern did not dominate most of the season as in 1991-92.

My analysis of snow statistics led me to be cautious in attributing a cause and effect relationship between El Nino and the numbers below. The California 1982-83 results and the 1997 Southern Hemisphere weather fit the theory, but two seasons do not constitute statistical significance.

Another recent analysis of El Nino drew the analogy to flipping a biased coin. All the random factors which affect weather are still there, but the chances of a southern or split storm track or greater intensity than normal are increased. There is still a reduced but significant chance that the expected events will not occur. Thus, when forecasters include milder El Nino episodes than 1982-83 in their analyses, the effects are much less clear cut.

In summary, the 1997-98 winter weather conformed to El Nino expectations during about a third of the snow season, but to such a strong degree that season snow totals reflect its influence. In considering both 1982-83 and 1997-98, I suspect the El Nino coin has its strongest bias in Southern California, with the influence declining gradually as one moves north up the coast and more rapidly as one moves inland.

There is a mild tendency for the North American storm track to be strongest in Canada in December and move south to Utah and Colorado by March. Therefore El Nino effects are more probable in the second half of the ski season (February to April) than the first half (November to January). 1982-83 snowfall was more consistent than we saw in 1997-98 but it was still stronger in the second half. It snowed in the Sierra every weekend from January 15 to May 15 in 1983. For more details on 1997-98, see 1997-98 Season Analysis and 1997-98 Ski Season Summary.

RECORD HIGH (10 Years Minimum) RECORD HIGH (10 Years Minimum)
Central Sierra Snow Lab - Boreal, Cal. 7,200 676 Sun Valley, Idaho 8,800 232 Dec.-Mar.
Kirkwood (Carson Pass), Calif. 8,526 788
Southern California Composite 7,000 - 8,000 264
Berthoud Pass, Colo. 11,315 362 Squaw Valley, Calif. 6,200 352 Dec.-Mar.
Alta, Utah 8,650 630 Teton Pass, Wyo. 8,000 254 Dec.-Mar.
Mammoth Mtn, Calif. 9,600 or 8,900 567 Big White, B. C. 6,200 219 Dec.-Mar.
Mt. Bachelor, Ore. 6,350 536 Sugar Bowl, Calif. 7,000 551 Dec.-Mar.
Loveland, Colo. 11,200 417 Big Sky 1, Mont. 8,000 212 Dec.-Mar.
Snow Basin, Utah 7,700 409 Crystal Mtn 2, Wash. 6,100 325 Dec.-Mar.
Alpine Meadows, Calif. 7,000 606
Arapahoe Basin, Colo. 10,820 418
Taos, N. Mex. 11,200 304 Vail, Colo. 11,250 261 Dec.-Mar.
Snowbird, Utah 10,000 538 Copper Mtn, Colo. 11,000 210 Dec.-Mar.
Brighton, Utah 8,740 452 Aspen Mtn, Colo. 11,190 181 Dec.-Mar.
Mary Jane at Winter Park, Colo. 10,800 393 Red Mt. Pass, Colo. 11,090 256 Dec.-Mar.
Winter Park Base, Colo. 9,265 256 Wolf Creek, Colo. 10,642 286 Dec.-Mar.
Whistler Roundhouse, B. C. 6,000 404 Purgatory, Colo. 10,000 185 Dec.-Mar.
Park City 1, Utah 7,140 158 Tod Mt. (Sun Peaks), B. C. 6,100 150 Dec.-Mar.
Arizona Snowbowl 1, Ariz. 9,500 215
Arizona Snowbowl 2, Ariz. 10,800 275
Mt. Rainier Paradise, Wash. 5,420 581 Crested Butte, Colo. 10,150 136 Dec.-Mar.
Stowe, Vt. 3,950 198 Bridger Bowl, Mont. 7,100 181 Dec.-Mar.
Sunshine Village, Alb. 7,028 188 Stevens Pass, Wash. 4,061 296 Dec.-Mar.
Mt. Norquay, Alb. 5,350 82 Sunlight, Colo. 151 Dec.-Mar.
Cannon Mt., N. H. 1,800 112 Crystal Mtn 1, Wash. 4,400 208 Dec.-Mar.
Sugarloaf, Maine 3,695 138 Snoqualmie Pass, Wash. 3,000 237 Dec.-Mar.
Jackson Hole, Wyo. 8,250 350
Gothic, Colo. 9,400 332
Alyeska, Alaska 1,400 477
Monarch, Colo. 259
Blackcomb, B. C. 5,002 341
Thompson Pass (Chugach), Alaska 2,450 368
Lake Louise, Alb. 6,700 120
Mt. Washington, N. H. 6,262 188 Schweitzer, Idaho 138 Dec.-Mar.
Killington, Vt. 4,241 197
Mt. Fidelity, B. C. 6,150 414
Whistler Base, B. C. 2,200 128
Steamboat, Colo. 9,200 232
Jay Peak, Vt. 3,000 247
Whiteface (Lake Placid), N. Y. 3,660 48
RECORD LOW (10 Years Minimum)