76 AUSTRALIAN WEATHER. 



storms and rains were not so general as on the thunderstorm 

 type, but curiously, were recorded in an almost parallel area of 

 country, nearly three hundred miles wide by twelve hundred 

 long. Though great barometric changes have taken place, the 

 pressures remain about the same as on Chart No. 1 3. 



TYPE VII. A RAIN STORM WITH VERTICAL AND NEARLY STRAIGHT 



ISOBARS. 



This type is one of the best defined and reliable of the series 

 for forecasting purposes, because with them, good general rains 

 almost invariably come. They are the rear isobars of a departing 

 anticyclone, and the wind circulation from north and north-east 

 brings into the interior winds laden with tropical moisture to 

 meet in the west southerly winds laden with antarctic cold, 

 and therefore precipitating power. The sequence of rain is 

 rendered even more certain if rain be recorded in the north-east 

 before the isobars straighten, or in the \ depression to the south. 



The actual height of the barometers is not material, but the 

 greater the number of isobars in a given area, the more extensive 

 will be the rainfall ; the rain usually lasts three days. The rain 

 begins to fall north-west of New South Wales, spreads southwards, 

 then eastward, and finally northwards, crossing the mountains 

 near the Queensland boundary. A fine example of this type 

 occurred on 15th, 16th, and 17th October, 1894. (Charts 16, 17.) 



On the 15th, Chart 16, a departing anticyclone rests over 

 Tasman Sea, and its rear isobars are shown running north and 

 south over central Australia ; another anticyclone is shown over 

 Western Australia and a A depression east of the Australian 

 Bight ; a trough of low pressure rests over Central Australia from 

 north to south. On this day the only indications of the 'pending 

 rain were found in the cloudy skies generally over South Australia, 

 western parts of New South Wales and Queensland, and a small 

 area of rain in South Australia. 



In Chart 16, the straight isobars of Chart 15 have entirely 

 disappeared, but the rain has come over Central and South 



