El Nino Southern Oscillation (ENSO) Index. Red indicates El Nino (warm phase) and blue indicates La Nina (cool phase).
El Nino Southern Oscillation (ENSO) Index. Red indicates El Nino (warm phase) and blue indicates La Nina (cool phase).

The topic of El Nino or La Nina and how they relate to our weather and snow conditions is a very popular one. Experts have been predicting that an El Nino pattern will develop this fall or winter, which has led many avid skiers/riders to panic slightly (at least inwardly). Will this season be one to forget or is there just too much hype around El Nino and La Nina?

What is El Nino? El Nino refers to the warm phase of the El Nino Southern Oscillation (ENSO), while La Nina refers to the cool phase. During El Nino there is above normal sea-surface temperatures in east-central Equatorial Pacific, and in La Nina the opposite is true. The changes in sea-surface temperature result in changes in atmospheric circulation patterns and can lead to dramatic changes in weather patterns around the world. The notable weather impacts on the West Coast of North America are much wetter conditions in California, and generally warmer and slightly drier conditions in Washington and BC.

The current sea-surface temperatures in the eastern-central Equatorial Pacific indicate a likely El Nino scenario. What about the unusually warm waters off the coast of N. America?
The current sea-surface temperatures in the eastern-central Equatorial Pacific indicate a likely El Nino scenario. What about the unusually warm waters off the coast of N. America?

The image above shows sea-surface temperature anomalies. For ENSO we are focusing on temperatures in Equatorial Pacific. What about the near-record warm temperatures shown on the West Coast of North America? Maybe this will have an impact on our weather? The waters are over 3 degrees Celsius above normal!

Recently I had a news reporter ask me what I thought an ‘El Nino winter’ means for avalanche and snow conditions in Western Canada. This is a tough question to answer in a short TV clip. I always think back to a famous climate quote, “climate is what you expect, weather is what you get”. Avalanches are driven by weather, but there are patterns based on climate. The correlation between El Nino and our weather and local avalanche conditions isn’t super strong. On average we could see slightly warmer and drier than normal conditions. So far in December we’ve seen cold dry weather and warm and very wet weather, which has led to a slightly warmer and drier December than average.

There is one recent study (D. McClung, Effects of El Nino and La Nina on Snow Avalanche Patterns, 2012) which states that the temperature effects of El Nino are most notable at lower elevations in the maritime climate. If this is true it would make sense that El Nino is very bad for snow enthusiast and businesses on the North Shore Mountains. Slightly warmer temperatures can drive freezing levels just above the summits of the local hills (around 1300-1400 m) resulting in much more rain and lower snowpack depths.

If we look back at past El Nino and La Nina events and compare the snowpack depth for January 1 at Grouse Mountain we can see a trend. The average snowpack depth is below normal during El Nino years and above normal for La Nina Years. Of course, if you look at the 8 lowest snowpack years (for Jan 1) you will see that 6 of the 8 seasons were ENSO neutral, one was El Nino, and one was La Nina. El Nino or La Nina does not guarantee what kind of winter we will see.

 

A look at recent El Nino and La Nina winters and snowpack depths at Grouse Mountain (Jan. 1).
A look at recent El Nino and La Nina winters and snowpack depths at Grouse Mountain (Jan. 1).

So, are we experiencing El Nino this year and is this the reason my skis haven’t seen the snow yet? Despite a complete lack of snow on the North Shore Mountains (in mid-December!), we are still not officially experiencing El Nino. Apparently we are in an ENSO neutral phase and an ‘El Nino Watch’. Experts are saying there is a 65% chance we will see a weak El Nino event this winter. The sea-surface temperatures in the east-central Pacific are warm, but the atmosphere is yet to sync up and drive a typical El Nino weather pattern.

Temperature outlook for December 2014 to February 2015. It looks like it should be warmer than normal.
Temperature outlook for December 2014 to February 2015. It looks like it should be warmer than normal.

The latest probabilistic weather outlook is still calling for above normal temperatures on the BC coast, with slightly less than normal precipitation. That being said, you never really know how it will pan out. It could just be a late start to the season and maybe we will see our best snow in March and April. Maybe we’ll have to hit the road to find good snow. Time will tell…

EL NIÑO: Does this mean no snow on the North Shore?

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