When Are We Getting Snow Again This Year
Commonwealth of australia's snow season is notoriously fickle. Some years bring deep cover lasting for virtually six months (such equally in 1964). Others barely embrace the grass for a few weeks (such every bit in 2006).
The difference between a adept season and a bad one may exist a single conditions event, such every bit the so-called Snowmageddon in 2014, which dropped around a metre of snowfall in less than a calendar week.
The high variability of the snow season means the Bureau of Meteorology doesn't currently produce a seasonal outlook for snow (as nosotros practise for temperature and rainfall). Even so, we know that the same climate drivers that affect Australia's weather as well influence our snowfall.
El Niño and La Niña
The best way to see how snowfall varies from yr to year is to apply data from Spencers Creek in the New South Wales Snowy Mountains, a pristine site 1,830 metres in a higher place sea level. Past studies bear witness that these data tend to correlate with snow more than generally across the mainland alpine regions, only they don't always match the cover at lower elevations.
First, let'southward look at El Niño. Nosotros are coming out of one of the strongest El Niño events on tape. During El Niño years, rainfall is typically below average across eastern Australia during the snow season, and temperatures are warmer during the 24-hour interval. The maximum snow depth averages about 35cm less than the all-years average, while the menstruation with more than 100cm is about two weeks shorter.
El Niño'south opposite, La Niña, usually brings above-boilerplate rainfall, but this doesn't necessarily mean more snow. Temperatures tin can sometimes exist too loftier and hence atmospheric precipitation may autumn every bit rain fifty-fifty at higher elevations, which tin actually subtract snow depths.
This has happened more frequently in recent decades equally a result of climate modify. Seven of the past eight La Niña years accept produced lower maximum snow depths than average.
Historically, neutral years have had more consistent practiced snowfall depths than either El Niño or La Niña years.
It is important to consider these drivers as tilting the odds towards a particular upshot, rather than guaranteeing it. While about half the historical El Niño years have had well-below-average snow, 3 El Niño years had well-higher up-average snow depths: 1972, 1977 and 1991. That said, no recent El Niño year has produced skillful snowfall, with these winters tending to exist peculiarly dry.
The other players
To make things more complicated, El Niño and La Niña don't human action alone.
The Indian Ocean Dipole (IOD) may really be a clearer indicator of snow depth. Similarly to El Niño, positive IOD years tend to exist drier than average across southeastern and central Commonwealth of australia, leading to lower snowfall depths. They are particularly dry over the Australian Alps when El Niño and positive IOD events coincide.
Unsurprisingly, snowfall depths in late winter and leap are also lower when the IOD is positive. Snow depths are generally college than average during years with a negative IOD.
The Southern Annular Mode (SAM) has the strongest relationship with snowfall. Common cold fronts and low pressure systems are the principal atmospheric condition systems that bring our snow, and the SAM indicates whether the westerlies that bring this weather are closer to Commonwealth of australia or the poles.
Negative SAM brings the fronts, rain and snowfall further north, while during a positive SAM these fronts move further southward. The average (mean) maximum snowfall depth in negative SAM years is a absurd 240cm, almost 80cm higher than in positive years. Unfortunately, accurate forecasts for SAM are even so but possible for two to three weeks alee, which ways that this measure out is more of a diagnostic rather than a forecasting tool.
Of course, climate change likewise plays a role. Both maximum snow depth and total snowfall accumulation take declined over the past 25 years. The reduction in snowfall cover is virtually obvious at lower elevations and at the end of the ski season when warm spring rains can hasten the melt.
Still, while it has been a few decades since the concluding iii-metre year (in 1992), there are still above-average seasons when the weather and climate is correct, most recently in 2019, 2022 and 2022 all exceeding 2-metre snow depth.
Less moisture? Never fright, snowmaking is hither
El Niño, positive IOD and positive SAM periods all typically atomic number 82 to less wet in the air, which partly explains the lower snowfalls. But with less deject to trap in the heat at nighttime, they also accept lower minimum temperatures.
Luckily for snowriders, these are likewise the ingredients for good snowmaking and tin contribute to less snow melting. The power to harvest snow and movement it where needed can besides allow ski resorts to moderate the impacts of average or below-average natural snow embrace on skiers and snowboarders.
What's alee for the adjacent snow season?
While forecasts for the Southern Annular Style just have skill for a few weeks ahead, forecasts of ENSO and the IOD can provide some insight into the futurity snow season and conditions. As we head into wintertime it's good to cheque whether the ENSO and IOD forecasts might be agile and take a possible influence during the snow flavor. ENSO and IOD forecast skill improves during winter so keep runway of any changes to the outlooks of climate drivers for the season ahead.
Finally, a word of circumspection. Don't get besides excited by early snowfalls, or indeed sell your skis if winter starts with no cover: ii of the all-time seasons on tape – 1956 and 1981 – had no snowfall at all at the start of June, while two of the poorest seasons – 2006 and 1965 – had 20cm and 60cm, respectively, of snowfall on the footing before the Queen's Birthday weekend. Early-flavour cover isn't always the guide we might think it is.
While nosotros know the Australian snow season can certainly have large variations in its snow cover, knowing the country of Australia's climate drivers can give a heads-upwardly on what the season may be like. Simply remember, at that place are always exceptions to the rules.
For the about up-to-engagement information on climate drivers, check out our Climate Commuter Update. Read further analysis here.
Authors
Catherine Ganter, Senior Climatologist, Australian Bureau of Meteorology; Acacia Pepler, Climatologist, Australian Bureau of Meteorology; Andrew B. Watkins, Director of Climate Prediction Services, Australian Bureau of Meteorology; Blair Trewin, Climatologist, National Climate Centre, Australian Bureau of Meteorology, and David Jones, Scientist, Australian Bureau of Meteorology
This article was originally published on The Chat and updated in August 2020. Read the original article.
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Source: http://www.bom.gov.au/climate/updates/articles/a016.shtml
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