NOAA briefing on La Nina - strongest since 1955

http://www.srh.noaa.gov/abq/?n=specialwebbriefing

Highlights:

• "Off the chart drop. Approaching levels not seen since 1955."
• Further strengthening predicted
• "Moderate to strong La Niña conditions are likely to persist into Spring 2011."
• Pacific Northwest will get "hammered" more by the resulting storm track
• Winter storms seem to miss the southern tier of the country
• From a purely selfish perspective, I'm thrilled to see the winter precipitation forecast Dec.-Mar. in the northern Wasatch slightly above normal with relatively near-normal temperatures.

strongest since 1955

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at this time of year. But strongest since 1975 at any time of year.

At any rate PNW, northern Rockies and western Canada are close to guaranteed above average seasons. As always, do not take these predictions to mean much for your specific ski vacation week, or even a whole month. There is a mild tendency for the impact to be strongest in the front end of the season, which raises the odds some for advance planners.

That New Mexico link was interesting. The only data I have is from Taos, where impact is in the mild-to-moderate category, while from that data it's clearly stronger in the central/southern part of the state.

Tony,

Was 2005-06 a La Nina year? This fall feels similar to me so far... Way hot & dry in early fall and that year I seem to remember had a big Nov-Jan before tapering off a bit Feb & March - At least for central Colo. I think snowfall around here was above average though not too crazy since Feb-April was a bit lower than average.

EMSC":10uin1qz said:

Was 2005-06 a La Nina year?

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Not by most definitions. In MEI values it ranks #21 out of the 60 years of data, about 1/3 the La Nina strength of 2007-08.

I'm not a big fan of the analog method of predicting weather, but 2010 looks a whole lot like 1973 in terms of the MEI so far. 1972-73 was the 6th highest El Nino; 2009-10 was 7th highest. 1973-74 was THE highest overall La Nina of the 60 years of data. If the MEI maintains its JUL/AUG level of -1.81 all the way through the northern ski season, it would exceed 1973-74. The implication of admin's original reference was that La Nina by other more timely measures than MEI is continuing to strengthen in September.

How was the 73-74 season for Mammoth? I know a strong La Nina generally means a slow start and early spring for Mammoth, but this year seems so extreme that it may have a larger chance to diverge from historical trends.

I have recently incorporated tracking of snowfall months (December to March only) with MEI reading >.750 or <-.750. For Mammoth there are 31 months with MEI<-.750 and snowfall averages 88.7% of normal during those months. Mammoth's entire 1973-74 season was 86% of normal, right in line with the overall La Nina picture. With regard to incidence, most of the months in 1973-74 were close to or even a bit above normal except for a very dry February with only 9 inches. This reinforces my belief that La Nina is a bias in the weather that is likely to assert itself on occasion during the season but that one cannot predict in advance precisely when.

Larry Schick believes that La Nina works more like an on/off switch; once a certain threshold is reached (probably in the -.750 to -1.000 range) the expected weather effects are likely. He believes that El Nino effects are more sensitive to increasing strength, thus the largest effects were in the 2 big seasons in 1982-83 and 1997-98. 1998-99, which produced the Mt. Baker world record and numerous other spectacular snow numbers in the Pacific Northwest and western Canada http://webpages.charter.net/tcrocker818/summ99.htm, was only the 9th strongest La Nina.

I don't have that much data from 1973-74, but for those interested:

1973-1974 SKI SEASON SNOWFALL SUMMARY

RECORD HIGH (10 Years Minimum)
Whistler Base, B. C. 2,200 425
Bridger Bowl, Mont. 7,100 319 Dec.-Mar.
Tod Mt. (Sun Peaks), B. C. 6,100 201 Dec.-Mar.

HIGH
Mt. Rainier Paradise, Wash. 5,420 968
Crater Lake (Mt. Bailey), Ore. 6,800 576
Berthoud Pass, Colo. 11,315 376
Sunshine Village, Alb. 7,028 293
Jackson Hole, Wyo. 8,250 494
Mt. Bachelor, Ore. 6,350 534
Lake Louise, Alb. 6,700 173
Vail, Colo. 11,250 330 Dec.-Mar.
Big Sky, Mont. 8,920 261 Dec.-Mar.
Whistler Roundhouse, B. C. 6,000 479 Dec.-Mar.

ABOVE AVERAGE
Mt. Washington, N. H. 6,262 367
Central Sierra Snow Lab - Boreal, Cal. 7,200 463
Alta, Utah 8,650 590
Mt. Fidelity, B. C. 6,150 589
Snowbird, Utah 10,000 558
Mt. Norquay, Alb. 5,350 130
Park City 2, Utah 9,280 312
Crested Butte, Colo. 10,150 183 Dec.-Mar.
Copper Mtn, Colo. 11,000 222 Dec.-Mar.

BELOW AVERAGE
Mammoth Mtn, Calif. 9,600 or 8,900 311
Stowe, Vt. 3,950 207
Taos, N. Mex. 11,200 216
Loveland, Colo. 11,200 339
Sugarloaf, Maine 3,695 120
Alpine Meadows, Calif. 7,000 349

LOW
Killington, Vt. 4,241 193
Thompson Pass (Chugach), Alaska 2,450 238

Tony Crocker":231ff41f said:

I don't have that much data from 1973-74, but for those interested:

1973-1974 SKI SEASON SNOWFALL SUMMARY

RECORD HIGH (10 Years Minimum)
none in Colo llisted

HIGH
Berthoud Pass, Colo. 11,315 376
Vail, Colo. 11,250 330 Dec.-Mar.

ABOVE AVERAGE
Crested Butte, Colo. 10,150 183 Dec.-Mar.
Copper Mtn, Colo. 11,000 222 Dec.-Mar.

BELOW AVERAGE
Loveland, Colo. 11,200 339

LOW
None in Colo

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Now that's quite the trick. From high to below average all in the same basic region of Colo. Obviously storm direction impacted the final results for central Colo. Specifically I'm going to guess a lot of due west to east storms and lower than normal upslope events based on those areas.

EMSC":i5fjismi said:

From high to below average all in the same basic region of Colo.

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It's random. Steamboat is up there on the same storm track as Jackson and thus benefits from La Nina. The other places not much. Variation is due to other factors.