572 



Principles of Weather Forecasting. 



while if it approaches the center from the west it can only 

 do so by traveling eastward faster than the earth itself and 

 f.hese changes in velocity cause winds from the west to 

 move toward the equator side of the storm center, while 

 those from the east always go to the polar side. The effect 

 is tlie same as would result from checking or increasing 



FIG. 266. Diagram of upper winds iu a typical cyclone. (After Ferrel.) 



the rate of rotation of the earth upon its axis. Making 

 it rotate faster would throw the air and water also toward 

 the equator, while slackening its speed would permit both 

 air and water to move toward the poles. 



727. Progressive Movements of Storms. Cyclonic storms 

 in all parts of the world have a progressive movement 



