296 



PHYSIOGRAPHY 



The strength of the storm was exceptional, and its course unusual, 

 as will be seen by comparing Fig. 253 with Fig. 252. 



Tropical cyclones do not occur in the South Atlantic, but in the 

 Pacific they occur on both sides of the equator. They occur in 

 the later part of the hot season of the latitudes where they occur. 

 The tropical cyclones of the North Pacific start in the vicinity of 



Fig. 252. Course of West Indian storms for August, September, and Octo- 

 ber, 1878-1900. The lighter lines show the tracks of individual storms, 

 the heavy line the mean course. (U. S. Weather Bureau.) 



the Philippines, and sweep the coast of China, and are called 

 typhoons. 



Weather predictions. Weather predictions are based on the 

 facts shown on weather maps. Take, for example, the map of the 

 25th of September, 1903 (Fig. 246). Rain accompanies the cyclone 

 which is central over Dakota. Since this storm has, for the last 

 24 hours, been, moving a little south of east at the rate of about 

 40 miles an hour, it is fair to presume that it will move in this same 

 general direction at a similar rate for the next 24 hours. If, in 

 this time, it advances to the Lake Superior region, it will probably 



