Page:Hunt - The climate and weather of Australia - 1913.djvu/150

Rh the 9th, about the lowest on record there for October. Probably the real significance of the phenomenon lies in the fall of pressure which took place from the southwards between the 8th and the 10th, causing the 30.0 isobar which lay east and west from Cape Borda to Gabo Island on the 8th to turn as it were upon an axis so as to lie north and south less than 48 hours later. Over Northern Victoria the barometer fell from 30.1 to 29.7 within 24 hours from this cause, that is, to some impulse apparently coming from due south. The interesting question then arises, "To what extent was the cold and storm production generally due to rarefaction at the rain-producing levels?" The similarity between the phenomena of this storm and that of 28th September-1st October, 1908 (Figures 137-139) is worth noting. An examination of five other cases of unusual cold with snowfall in Melbourne shows this tilting of the rear isobars of the "low" causing them to lie north and south to be a common feature. This involves a displacement of the following "high" centre from a normal position over South Australia to one several degrees further south, and the "high" is always an intense one.