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Chance of snow increases after a sunny, dry start to ski season

By Ben Deacon, Wednesday July 8, 2020 - 07:24 EST
ABC licensed image
The Australian Alps received a very welcome small snowfall on Friday and Saturday last week. - ABC licensed

Avid skiers may have been disappointed by poor snow falls leading into the school holidays, but there's some better news on the way with conditions tipped to become more favourable over the next few weeks.



It's been a tough year for Australia's ski fields — first there were bushfires, then COVID-19.

Since early June, a series of dry sunny weeks have crushed hopes of a bumper start to the ski season.

Senior climatologist and keen skier Agata Imielska, from the Bureau of Meteorology, noted the ski fields had a good dump of snow back in May.

"But then things really petered out," she said.

"Since then, we haven't really seen too much in the in a way of some really significant snowfall to really get the ski season started."



There were only 21 centimetres of snow recorded at the benchmark Spencers Creek snow gauge on July 1, which was below average for this time of year.



SAM leaves ski fields high and dry

Ms Imielska said the poor snowfalls were due to a lesser-known climate driver called the Southern Annular Mode, or SAM, which describes how far north weather systems in the Southern Ocean reach into Australia.

"During winter, positive SAM means that we generally see high pressure sitting over the country," she said.

"Because of that, those cold fronts just don't make it into the southern part of Australia."



SAM went negative last week, coinciding with a fresh fall of up to 20cm of snow last weekend.

This was good news for struggling ski resorts that have had to rely on snowmaking for the make-or-break school holiday period.

A further 10-15cm of snow has been forecast for the coming weekend.

SAM is predicted to remain negative or neutral for the next week or two, raising hopes for better skiing.

"Overall I'd say it's looking good, given we're not seeing the really strong positive SAM values from mid-June," Ms Imielska said.

But SAM cannot be reliably forecast any further in advance.



"SAM is more something that we look at as to what's going to happen in the next week or two," Ms Imielksa said.

"Sometimes, there might be quite good and strong agreement in terms of what we might be expecting over two weeks.

"But usually one week is a pretty good indication of what we might see."

Why Australian ski seasons are so hard to predict

Ms Imielska cautioned against making predictions on the skiing conditions beyond two weeks because a small number of significant weather events can make or break season.

"We've had years where some major cold fronts come through, bringing up to a metre of snow within a very short space of time," she said.

"Conversely, we've had rain events come through that wash some of that snow away."

Current technology still cannot make useful forecasts of single weather events more than a week or two in advance, and until that improves accurate long-term snow forecasts will not be possible.



Great ski seasons even in drought years

According to the Bureau of Meteorology, the past three years have seen some of the worst winter droughts on record in south-eastern Australia, but the last three ski seasons were all above average.



Ms Imielska said the seasonal outlook for more rain in Australia due to La Nina might not necessarily translate into a better ski season.

"If we get the right weather system, we can see that coming through as a really good snow dump, for example," she said.

"But if things aren't quite cold enough, then that extra moisture can fall as rain.



"This both has the potential for great snow but also has potential to wash some of that snow away — it's a bit of a double-edged sword."

Looking back over previous ski seasons, Ms Imielska observed Australia's most reliable ski seasons happened in years when the El Nino/La Nina and Indian Ocean Dipole cycles were both in neutral.

"'Reliable' doesn't mean that it's necessarily the best snow season," she said.

"It just tends to just be that bit more reliable."


- ABC

© ABC 2020

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