576 



Principles of Weather Forecasting. 



the passage of cyclones across the United States lies usu- 

 ally in advance of the central LOW, much as represented 

 by the heavily shaded area in the diagram Fig. 269, and 

 at a distance of 200 to 700 miles from the center. 



In this area the precipitation is most continuous and 

 steady over the eastern and northern portion, where the 

 surface winds range from S. E. to N". E. in direction. To 

 the southeast and south of the low center, where the winds 

 are S. and S. W., there is a general tendency for the pre- 

 cipitation to occur in the form of showers, to be more vio- 

 lent in character, and local rather than wide spread. 



Fio. 269. Diagram of storui area. 



733. The Origin of Ordinary Storms. There is as yot no 

 general agreement among students of meteorology regard- 



