After some decent early snowfall in the week leading up to the official start to the Australian ski season, the resorts look set to endure a lack lustre June with no new wintry falls on the horizon.
The season which runs from the Queen’s birthday holiday in June to early September can be fickle at the best of times culminating in brief periods of sizeable accumulations inter changed with longer episodes of reduced activity.
The following chart shows the coldest of the air contracted well south of the Australian continent, kept in check by a band a strong winds that circumnavigated the polar region.
A combination of the Earth’s rotation and lessening of the polar jet stream allow this colder air to surge northward in the form of undulating wave like patterns around the Antarctic continent
It is the associated cold air with these systems during the darker months that bring the prospect of wintry weather for the Australian ski resorts and even low levels also.
Interpreting the charts
The Thickness lines indicate the average temperature through the lower 5km or so of the atmosphere. They measure the distance in dekametres (tens of metres) between the 1000 and 500 hPa pressure levels.
The average distance is about 5.5km, or 5500 metres or 550 dekametres, which are the measures shown on the map.
Warm air is thicker than cold air, so lines marked 560 (or 5.6km) and above indicate that the bottom 5km or so of the atmosphere is fairly warm.
A thickness below 540 (or 5.4km) indicates a pretty cold lower atmosphere, and below 530 is really cold!
In colder air masses the freezing level is lower thus any frozen precipitation can reach the surface as snow without melting.
The 540 line highlighted in “blue” on this chart is often used as a rough guide to determine when an air mass is cold enough to produce snowfalls on the Australian Alpine areas.
The overlaid “white” hatched shading indicates where wintry precipitation possible down to surface level.
Any more Snow on the horizon
Present indications suggest the current pattern will remain in place for the rest of June with the more significant weather systems expected to continue to track well to the south of mainland, thus equating to little in the way of decent snowfall on the forecast for the Australian ski resorts.