METEOROLOGICAL WORK IN AUSTRALIA, 265 



or latitude of this anticyclonic belt depends on the time of the year, 

 and varies in different years. Normally, during the winter the crest 

 of the "high " lies over the interior, approximately about latitude 

 29° or 30° fvide map 6). North of this the continent is swept by 

 the dry south-east trade winds, whilst to the south we have, in South. 

 Australia, a prevalence of dry northerly (north-east to north-west) 

 winds, varied by strong west and south-Avest winds as coastal 

 depressions pass from west to east, with rain and squally weather. 

 On the east coast west winds prevail during the winter. 



The character of ovu- winter season, in South Australia especially, 

 depends very ch)sely on the position of this wall, as it were, of 

 high barometers, which plays a very important part in Australian 

 climate. If it lies too far south, or near the coast, the winter over 

 the southern districts of the colony (I am speaking of South Aus- 

 tralia) is dry, but we may, and. occasionally do, have under these 

 conditions good rains in the north, due to the extension of tropical 

 depressions bringing rain over the interior of Queensland, New 

 South Wales, and South Australia east of Lake Eyre and the 

 Flinders Range. 



On the other hand, if the anticyclonic areas keep more to the 

 north, the southern or coastal V depressions extend further 

 inland, at times being felt as far as the tropics, and we haA-e 

 copious rains all over the colony, a^^ well as in Victoria and western 

 ^evv South Wales. As the depressions pass the winds veer from 

 north-east and north to north-west, west, and south-west. Steady 

 rains set in with the wind at north-east to north, heaviest at north- 

 Avest. and. break up with heaA-y shoAvers and squalls at south-Avest, 

 -'sometimes accompanied by heavy thunderstorms, AA^hile the Avind. 

 is iiorth-west to south-we-t. 



As the sunmier advances the high pressure belt retreats, and 

 usually lies a little to the south of the coast, Avith its maximum 

 pressure about latitude 37° to 40°, and the Avhole of the interior of 

 Australia is then Avell within the equatorial belt of Ioav pressure. 



On the north coast, and for some distance inland, the winds are 

 uorth-Avest, monsoonal rains setting in at the end of October and 

 lasting till the end of March or April, the heaA'iest rain being in 

 December, January, and February, in which months the aAerage at 

 Port Darwin is 10-420, 14-782, and 13-009 inches, respectively. 



The southerly reach of the north-Avest monsoon depends on the 

 pressure in the interior, Avhich is frequently A'ery uniform, but 

 when a barometric valley fvide maps 4 and 5) is formed the rains 

 may extend almost witbout a break right across the continent, 

 being in some years very heavy and general in South Australia. 

 ■On the east coast summer rains are frequent and heavy, especially 

 A\-hen troi^ical •' Ioavs " pass down from the north and north-east 

 fvide maps 2 and 3). 



In South Australia the prevailing wind in summer is south-east, 

 varied by hot, dry, northerly winds, as coastal "lows" approach 



