WEATHER FORECASTING. 59 



rain falling, so that in such a case rain should be forecast for 

 the south coast from Cape Agulhas to the Eastern Province, 

 extending inland. 



The foregoing is a general sequence of weather conditions 

 due to the passing of depressions. Two depressions are seldom 

 alike, and yet all are based on the same broad principle. 



Another form of depression is one of a cyclonic character 

 which affects the east coast and Natal. It is caused, no doubt, 

 by a cyclone in the Indian Ocean, moving from the north-east 

 and recurving in about the latitude of Durban. When such 

 a depression is seen to be to the north-east of Natal the winds 

 there blow easterly and pressure decreases, the heat often 

 becomes intense, especially as the V from the depression 

 pushes down over the land between the sea coast and the high 

 mountain chain. When pressure begins to increase, the wind 

 goes to the south-west and the change is usually accompanied 

 by heavy downpours of rain and violent thunderstorms. Often 

 these affect the coast lands as far as the south-east of the Cape 

 Province. 



Normal fine weather conditions exist when a belt of mean 

 pressure rests over the south coast lands from the south-west 

 to Natal, with areas of higher pressure over the South-West 

 Ocean and Eastern Transvaal. Pressure must not be increasing 

 or decreasing rapidly. When such a condition exists the forecast 

 is for fine weather generally, winds southerly over the south- 

 west, westerly along the south coast, south-westerly at Natal, 

 and northerly in the Transvaal and the Free State. Then watch 

 the south-west for a change. 



The causes bringing rain over the Inland Plateau are some- 

 what obscure, but there seems reason to believe that after 

 pressure has been low and temperature warm, if a high pushes 

 up suddenly with steep gradients from the south coast to the 

 interior, accompanied by a fall of temperature, rain and thunder- 

 storms will prevail over the plateau. 



Areas of very high pressure are generally indicative of? 

 fine, clear weather, dry, hot days, and cool nights; light winds 

 and no rain. At the same time if secondary loops are found, 

 these will moderate the weather. 



When secondaries are passing they make their presence 

 known by cirro-cumulus in the sky; this is an unfailing portent; 

 when they pass to the south, generally moving from a westerly 

 to an easterly point, they are upon the northern gradients of an 

 anticyclone and cause indications of rain to disappear, at any 

 rate they make for fine weather, except that they increase the 

 intensity of south-east winds ; this is because their central and 

 southern regions are then the wet areas, their northern ones 

 being the homes of cirro-cumulus and following cirro-stratus 

 clouds. They seldom pass to the north of the Peninsula, but 



