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:

Spag_2015_8_25



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_2015_7_25

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).

1 comment to An extraordinary system

  • blakelindley

    good to have you back gerg i thought we’d lost you for a while there. Looking forward to riding out next weeks snow with you! Keep it coming Yew. This system’s delivered some waves for us this week, cant wait to see what its done to the hills this weekend.

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