130 The Sky 
is spoken of as a warm front; a cold air mass moving in to dis- 
place a warm one is called a cold front. Meteorological dis- 
turbances (windstorms, cyclones, thundershowers, etc.) are 
likely to be concentrated along a front. Warm and cold 
fronts each have characteristic kinds of storms. An approach- 
ing warm front will be heralded by the appearance of cirrus 
clouds in the sky. Gradually the clouds appear to get heavier; 
cirrus changes to cirrostratus, to altostratus, and finally to 
nimbostratus, with accompanying rainfall and temperature 
CYCLONE 
e anc) 
N 
AIR MOVING INTO state -/ 
ALOW DUE TO EARTH'S 
ROTATION 
rise. A cold front brings much more violent storms and hence. 
is of more concern at sea than a warm front is. No stratus 
clouds form, the first signs being altocumulus clouds which 
change to large thunderclouds, rain, and a temperature drop. 
Often there is a complete line of thunderstorms all along a 
cold front—a “line squall.” 
HURRICANES 
Air flows inward toward a center of low pressure. As it does | 
so its course is deflected because of the earth's rotation; as a ~ 
result it actually moves in a spiral path toward the low pres- — 
