More than any other holiday, a snow trip relies on the weather.
This is especially so in Australia where our modest mountains and latitude produce an infamously variable and short season.
Regrettably, El Niño is likely to occur this year and, along with other climate drivers, will likely create a below-average season in 2023, with warmer temperatures and less snowfall.
However, the fickle nature of an Australian season can often produce surprises.
Weather can make or break a snow holiday
Skiers and boarders hope for heavy snowfalls to build a deep snowpack that allows full access to a resort. They must also adapt to weather that can throw gales, rain, ice pellets, and white-outs in the mix.
In the very best years, such as 1964 and 1968, a deep cover of snow had already developed by early June, it continued to build further into winter, and it did not melt until late spring.
In the worst years, for example 1973 and 2006, even peak season only brought a patchy cover of snow on the higher slopes.
Veteran skiers in online forums recount horror stories from the time prior to snowmaking of carrying skis halfway down the mountain during lean seasons.
How snow seasons are measured
The most commonly used data for Australian snow is sourced from Spencers Creek where Snowy Hydro has taken weekly or biweekly snow-depth measurements since the 1950s.
Nestled high in the New South Wales Alps at an elevation of 1,830 metres, the site gives a reasonable indication of snow quality for the major resorts.
The highest-ever snow-depth reading (not necessarily the best season) was 361cm in early September 1981. The year with the lowest peak was 2006 when the depth only reached 85cm.
Can a snow season be predicted?
Changes in Indian and Pacific Ocean temperatures influence rainfall and temperature patterns across Australia, however, the relationship with snow depth is more complex.
For example, while La Niña boosts rainfall across south-east Australia by an average of 25 per cent, the increase in a season's peak snow depth at Spencers Creek only rises by 4 per cent.
This is because there is no guarantee the additional precipitation will fall as snow.
More indicative of a bumper season is the Indian Ocean. A negative Indian Ocean Dipole (IOD) event will on average increase the peak snow depth by 20 per cent.
As 2022 experienced a negative IOD, the season peak reached 232cm — 34cm above average.
Not surprisingly, El Niño or a positive IOD, which normally bring drought, lead to a reduction in snow depth of 17 per cent and 15 per cent respectively.
The worst scenario is both El Niño and a positive IOD in the same year. This leads to an average drop in snowfall of 23 per cent.
Predicting a snow season is difficult as it relies on an accurate forecast of the climate drivers. This is a challenge in autumn when seasonal forecasts are the least precise.
The other major influences are the frequency of cold fronts, which cannot be accurately predicted more than a few weeks ahead, and climate change, which is slowly eroding the snow season, particularly for lower resorts.
2023 season heading downhill
The signals from the oceans surrounding Australia currently indicate a lean snow season in 2023
If El Niño forms, a scenario now considered likely, then below-average snowfall becomes more probable. The average Spencers Creek peak snow depth in El Niño years had fallen to 165cm, but since 2000 has fallen to just 139cm.
If El Niño combines with a positive IOD, which models currently predict, then there is every chance this year could be one of the worst snow seasons in decades.
The only positive from a potential dry winter is an increase in the frequency of clear skies and, therefore, cold frosty nights; optimal conditions for snowmaking.
But if you are more satisfied with natural powder, then hope El Niño fails to eventuate and the Indian Ocean remains neutral.
Years without an active phase of the Pacific or Indian oceans have produced a much more fruitful average peak depth of 206cm, 8cm above the long-term average.
