SOUTHERLY BURSTERS. 21 



STRAIGHTENING OF ISOBARS AND RAIN. 



At the same time the rear isobars of this retreating high pressure 

 are becoming flatter or straighter, and causing a divergence of the 

 south-east trades which prevail almost constantly north of New 

 South Wales into a north-east wind. The result of this move- 

 ment is an inflow of humid air which penetrates into the southern 

 part of the continent as far as the South Australian border, and 

 sometimes still further west, that is, six to seven hundred miles. 



SOUTHERLY WIND THE PRECIPITATING AGENT. 



As the following high pressure approaches, the southerly or 

 surface precipating current in front of it travels eastward, and 

 meeting this humid atmosphere rain invariably falls inland, the 

 most copious downpour being along the western slopes of the 

 mountains. Ultimately this approaching anticyclone reaches the 

 eastern sea-board, thereby forcing the low pressure off and up the 

 coast, and by this time the wind which was southerly inland has 

 a tendency to veer to east following the isobars, and develops one 

 of the ordinary forms of easterly weather, which although some- 

 times dangerous to mariners by reason of its high winds and 

 stormy seas, is by no means so hazardous as the burster. The 

 wind rises gradually, ami thus several hours warning is given 

 before the disturbance assumes a serious aspect. 



A change of this character rarely makes itself felt beyond the 

 Queensland border. While the fury of the storm is spending 

 itself, the high pressure continues its forward motion south of the 



storm, the low pressure fills up, and the storm is over. 







The weather during the forty-eight hours preceding this change 

 may be, and generally is, locally hot and fine, but the develop- 

 ments in the twenty-four hours immediately antecedent to the 

 outbreak are exceedingly rapid. On the day of such a change the 

 weather reports, even from the inland districts, may tell of fine 

 weather, but by evening the disturbance is felt in the far west, 

 travelling with great speed towards the highlands, and during the 

 night, or by daybreak, it reaches the coast lands. 



