142 A YEAR IN SCIENCE 



a movement of air from the region of high pressure 

 toward the one of low. Such a movement is called a 

 cyclone. We must not think that a cyclone is always 

 a violent, destructive wind storm. Such storms are 

 correctly known as tornadoes. 



At the same time that there is a movement in toward 

 a region of low pressure, there is also an outward 

 movement from the area of high pressure. Such a 

 movement is known as an anticyclone. 



Because of the rotation of the earth, cyclonic winds 

 do not blow straight toward the center of the region 

 of low pressure. In. the northern hemisphere they 

 are deflected toward the right. (See Figure 53.) 



A region of low pressure is generally characterized 

 by rain, relatively high temperature, and shifting 

 winds. These conditions constitute a cyclonic storm. 

 A cyclone is not stationary, but moves generally in an 

 eastward or north eastward direction. As it moves 

 it is followed by an area of high pressure in which 

 the winds are moving spirally out from the center. 

 This anticyclone is associated with low temperature 

 and clear skies. Frequently during a cyclone so much 

 warm air from the south is brought into northern 

 regions that unseasonable warm weather follows. 

 Similarly, sometimes cold air spreads over a great area 

 extending south. When accompanied by a driving 

 snow r this constitutes a blizzard. 



Thunderstorms. We are all familiar with the char- 

 acteristic conditions of the atmosphere and sky pre- 



