查看完整版本 : 2011/12 La Nina

2011-10-25, 07:13
Just read the article in the Skiing magazine predicting the La Nina effect to North America this winter:

La Niña is back. This is good news for some mountains and bad news for others. And it’s actually really bad news for meteorologists, who now must answer the barrage of requests for a six-month snow forecast. Here’s the scoop on La Niña.

Water temperatures in the central Pacific Ocean are much colder than average, which is the definition of La Niña. Those temperatures can affect weather patterns across the globe, and that’s why La Niña is important. For North America, La Niña has some predictable consequences for snow during the winter: it snows a lot.

Last season, La Niña was moderate to strong, which translated into forecasts of much above average snowfall for the northern part of the U.S. and into Canada. For the most part, this forecast came true with nearly 150 percent of average snow falling in the Pacific Northwest and record seasons extending into Utah and northern Colorado.

However, this season’s La Niña is only about 60 percent as strong as last season. The tough part about this fact is that the forecast for snow isn’t as simple as lowering last season’s predictions by 1/3rd. When La Niña is strong, its affects on snowfall are rather predictable. When La Niña is weaker (or non-existent), it’s affects on our wintertime weather patterns are less certain, so the outlook for this season is much less confident.

British Columbia and Alaska often do well in La Niña years, with 10-25 percent above average snowfall. Even with a weaker La Niña this season, it still looks like these areas will experience plenty of powder.

Tahoe is always on the fence. La Niña usually means an active storm track through the Pacific Northwest. If these storms drop a bit further south, Tahoe gets the goods. This is what happened last season, with many areas reporting 150-200 percent of average snowfall. But this is a new year. We can hope for the best for Tahoe, but it’ll come down to the tracks of individual storms this season. The best bet right now is an average to slightly better than average season.

Utah and Colorado are much like Tahoe—on the fence. Northern Utah (where most of the resorts are, in the Wasatch) and northern Colorado (roughly north of Aspen) normally do well in La Niña years. Last season snowfall topped 150 percent of average, but I’m not overly confident about a repeat this year. The smart money would wager for an above-average season for these areas, but likely not as spectacular as last season.

Please note: This is only a prediction. Do check the local short term weather forecast.