Page:Hunt - The climate and weather of Australia - 1913.djvu/41

Rh (January) the centre of Australia is heated strongly and the winds on the north coast become much less constant, those from the west predominating. As the sun moves north again the wind changes to an easterly, and in June the south-easter is again dominant. It should be remembered that calms are very prevalent in this region.

2. The Queensland Coast (from Cape York to Brisbane) exhibits somewhat similar changes, but here are the most constant winds in Australia, for even in summer the wind merely veers from south-east to east. In January 40 per cent. of the winds are from the east and 30 per cent. from the south-east. In May 47 per cent. are from the south-east and 25 per cent. from the east. 3. The New South Wales Coast.—Here, as might be expected, the winds are very variable, for the region of the high pressure eddies is reached. Still there is some differentiation apparent. During midwinter (June, July, and August) there is, perhaps, a preponderance of south-west winds, due to the cold elevated area around Mt. Kosciusko. In midsummer (December, January, February) there is a similar local "monsoon" effect, giving rise to a strengthening of the north-east components. 4. The Southern Coasts, from Cape Howe to Cape Leeuwin, are on the border line between the high pressure belt and the region of prevailing westerlies. The centres of the Antarctic depressions moving from west to east—lie considerably south of our coasts; and hence these coasts are controlled by the north component (upper limb) of these depressions or eddies. Here the winds are westerly, and this fact probably accounts for the high aggregate of westerlies recorded in this region, although it is constantly traversed by circulating systems or cyclones.

5. The South-west Coast, from Cape Leeuwin to North-west Cape.—Here the winds throughout the year blow chiefly from south and west. A south-east component is more apparent during midsummer and autumn. The westerly component enters this region in winter, as the sun moves north and the southern "prevailing westerlies" swing northwards in unison and affect Western Australia. The two varying factors of south-east and south-west respectively are in fact but the result of the swing of the trade wind south in summer and of the westerlies north in winter. 6. The North-west Coast, from North-west Cape to Cambridge Gulf.—This region agrees fairly closely with the northern region. It is dominated by the south-east trade for eight months, but during midsummer the almost permanent "low" covering the hot Pilbara region in Western Australia gives rise to a "monsoon" and the coastal winds swing round from south-east to south-west. The south-east wind is, however, not so constant as that off the Queensland Coast, and in autumn (March, &c.) the winds are very variable. In the north calms are common, and except for the "willy-willies" storms are rare. The whole coast of Australia from Perth northward and east to Brisbane is at times influenced by the South-east Trade, so that a résumé of the movements of this important air current will be of interest.