Season 2017 roundup

You may need a browser refresh to see the latest charts.

After one of the worst season starts on record (fifth-worst, on my assessment) 2017 morphed into a ripper, with the biggest high-altitude peak snow depth in 17 years — 240.9 cm, vs 262 cm way back in 2000.

Spencers Creek snow depth, from Snowy Hydro

 
Once again, lower altitudes weren’t as impressive, with Deep Creek (south of Cabramurra, 1620 m) just pipping 2014 to record its highest peak since 2008, and Three Mile Dam (near Selwyn Snowfileds, 1430 m) failing to even beat last year.

Deep Creek snow depth

Deep Creek snow depth, from Snowy Hydro

Three Mile Dam snow depth

Three Mile Dam snow depth, from Snowy Hydro

 

The prediction

I predict the season peak snow depth at Spencers Creek¹ using a simple seven-parameter multiple regression model based on well-known climatic modes and influences.

My pre-season prediction for 2017, made in early May, was an absolute shocker. It was for a peak depth of just 163 ± 44 cm vs the outcome at 240.9 cm. Adjusting for the actual parameter outcomes (rather than using my pre-season guesses) helps a bit, lifting the prediction to 187 cm, still well outside my plus/minus one standard deviation error estimate. Realistically, only about two thirds of seasons would be expected to fall within that error band, so finding one that doesn’t isn’t any surprise.

The long term hindcasted ‘prediction’ vs performance of my model now looks like this:

Spencers Creek season peak snow depth – hindcast ‘prediction’ vs performance

 

Influences

The main climatic parameters were fairly neutral for 2017 (see highlighted points in the correlations chart below). Sea surface temperature in our area of interest was below trend despite a record hot Tasman Sea later in the year (indicating a cooler than trend Great Australian Bight).

Snow depth prediction model SST influence box

Winter sea surface temperature trend

 
The very slow season start was due to the driest June on record in Victoria

The Bureau of Meteorology doesn’t really offer a cogent explanation for that. Then the weather broke and a vigorous westerly flow across the alps through August produced repeated heavy falls. That change too is not well-supported by the usual indicators, for example SAM/AAO remained mostly positive, which does not usually suggest heavy snowfalls.

Antarctic oscillation

It was an unusual season.

 

The charts

The updated full records:

Snowy Hydro Australian snow depth records

Snowy Hydro Australian snow depth records

Snow depth record

Spencers Creek snow depth record

Spencers Creek snow depth anomalies

Spencers Creek snow depth anomalies

 

The season peak and integral depth:

Peak depth trend

Spencers Creek peak snow depth trend

Spencers Creek peak snow depth timing

Spencers Creek peak snow depth timing

Spencers Creek integral depth trend

Spencers Creek integral snow depth trend

 

The decades, and the future:

Future trend of Australian snow depth

Spencers Creek snow depth future

 

The correlations (2017 highlighted):

 

The dumps:

Spencers Creek "dumps"

When the dumps happen

 

Notes

1. Snow depth at ~1830 m elevation at Spencers Creek near Charlotte Pass, NSW, midway between Perisher Valley and Thredbo; data from Snowy Hydro Limited.

2 comments to Season 2017 roundup

  • There was depth last season at Spencer’s Creek but the length of the season was short with a late start and a rapid melt.
    Am I imagining it or has there been a rising trend in depth over the last 10 or twelve years at Spencer’s Creek?
    Also wondering, hoping, if we might have a phenomenon like in the northern hemisphere where I understand the warm air penetration into the arctic seemed to push very cold air into Europe and US. La Plagne in France has had a very early start, late finish and phenomenal depth this last season. So much so that the season is being extended to end 28 April.
    Thanks for graphs, I appreciate them very much. And enjoying the skiing while I still can and the snow line does not recede too far up the hill.

  • Roger W

    Fabulous analysis. Gives a clear picture of the factors influencing snow seasons. Keep up the good work.

Leave a Reply