In the upper reaches of the Southern Ocean, just below the Great Australian Bight, an enormous, spiralling stream of icy air churns eastward.

Before sun-up in a lounge room in suburban Wollongong, a man known as The Frog pores over satellite charts and data sets, plotting the path of this meteorological beast.

On a hunch, he can accurately predict when the monster highs will deliver the next major dump over the nation's ski fields - although not always so precisely how much snow will arrive.

Snow forecasting is at once an exact and inexact science, says Pete Taylor.