An extraordinary system

No, the snow depth peak is not already in; not by a long way. The weather this week has been extraordinary; so far from conventional Australian snow weather as to border on unprecedented. Does this look like snow weather:



No … yet that featureless polar pattern delivered up to 50 cm snowfall to the New South Wales alps in a continuous 36 hour fall (Victoria largely missed out — just 15cm):

Perisher Valley winterised automatic weather station precipitation record, from BOM



A large, complex and slow-moving — but not especially deep — low pressure system tracked right across the central Australian deserts from an extremely warm Indian Ocean, bringing huge amounts of moisture. The surprise for me, and I think many other seasoned observers, was that it arrived cold enough to produce mid- to high-level snow. Forecast-wise, both the NSW BOM and the impressive Jane Bunn had it spot on from a couple of days out. Others, well, not so good … I expected just rain. Here’s an animation of BOM’s surface chart archive, with a grab of the JAXA inferred precipitation intensity:

JAXA precipitation inferred from satellite imagery

BOM surface chart archive



You can see the interaction with a relatively strong polar front as the low crosses the continent, which may have helped deliver the requisite cold air.

The system has now reached the Tasman Sea and tightened into a more conventional east coast low, which is still bringing heavy rain to the NSW south coast and East Gippsland. Weather models have that combining with a further cold front tomorrow night (Thursday), for yet more snow … this time for Victoria as well as NSW, and to low levels.



I’m afraid my miserable pre-season peak snow depth prediction (141 ± 44 cm) is now shot, even before the strong system brewing up for next week arrives. Prediction is difficult… (no, that one wasn’t Yogi, or even Niels Bohr).