Page:Hunt - The climate and weather of Australia - 1913.djvu/111

Rh weather was anticipated, as this type of chart (19th) showing a deep cyclonic depression, wedged in between two energetic anticyclones, with isobars running approximately north and south, is a very favorable forerunner of widespread rains on the Australian continent, and the subsequent conditions more than realized these anticipations. Up to the 18th the disturbance was marked by heavy rains, though only moderate winds, but on that day it began to develop cyclonic and electrical energy, and its subsequent career was accompanied by most violent atmospheric commotion. On the night of the 18th violent thunderstorms, with fierce squalls and heavy rain, broke over the far north-western and western areas of South Australia, and rapidly swept across the State into Victoria, rain falling at 153 stations in South Australia up to 9 a.m. next morning (19th), of which 52 registered between ½ and 1 inch, and 55 over 1 inch (maximum, 168, at Streaky Bay, on the west coast), and at 135 stations in Victoria, of which 26 recorded between ½ and 1 inch, and 21 others over 1 inch (maximum, Dimboola, 183). The rain area had also widened considerably, for light rain was still falling in Western Australia, and commencing in Tasmania.

By the 20th the storm had reached its greatest intensity, its cyclonic centre being clearly shown to the south of Victoria and near the north-west corner of Tasmania (barometer at Stanley, 28.96 inches), with exceptionally steep gradients. Along the south-east coast of South Australia the previous night the weather was extremely wild, with winds of hurricane violence and exceptionally low barometers, and rain fell throughout the whole of South Australia, Victoria, Tasmania, and New South Wales, and extended into the south-west and south of Queensland, being recorded at 155 stations in South Australia, of which 56 registered from ½ to 1 inch, and 8 over 1 inch (maximum, Uraidla, 169); at 156 stations in Victoria, of which 55 had between ½ and 1 inch, 56 from 1 to 2 inches, and 18 others over 2 inches (maximum, Kyneton, 325); at 31 stations in Tasmania, 9 being from ½ to 1 inch, 9 from 1 to 2 inches, and 3 over 2 inches (maximum, Burnie, 271); at 140 stations in New South Wales, of which 46 records were between ½ and 1 inch, and 10 over 1 inch (maximum, Tumbarumbah, 181); and light falls at 44 stations in Queensland. The last chart of the series shows that the disturbance had passed eastwards to the Tasman Sea and become of a simple "Antarctic!" type while high pressures had become established over the continent. The isobaric distribution is of the ordinary winter type and fine weather returns.

A reference to the rain smears plotted with the isobars on Figs. 77-82 shows that it was in Victoria that the greatest overlap of the daily falls occurred. Hence, the ﬂoods were greatest in the rivers draining the Victorian highlands (see Fig. 76).

The series of heavy rains, accompanied by violent and prolonged thunderstorms, which set in over the western parts of this State in the early morning of the 19th August, gradually extended eastwards during the day, and was responsible for phenomenal floods in almost all the rivers in the western half of the State. These rains appear to have been at their greatest intensity along two parallel lines, one joining Warracknabeal and Queenscliff, the other Inglewood and Kyneton, and these give pretty nearly the direction in which the storm clouds were observed to be moving during the fifteen to twenty hours within which all the rain fell. East of Kyneton, the rains