Describe the characteristics, including where it forms, of
the following air masses:
Objectives P. 56
• Describe the formation of a front
• Differentiate among formation of a warm front,
cold front, stationary front, and occluded front.
• Describe weather patterns associated with each
type of front
When two air masses meet, they form a
front, which is a boundary that separates
two air masses.
• A warm front forms when warm air moves into
an area formerly covered by cooler air.
Formation of a Warm Front
A warm front forms when warm air glides up over a cold,
dense air mass. The affected area has warmer temperatures
and light to moderate precipitation.
• A cold front forms when cold, dense air moves
into a region occupied by warmer air.
Formation of a Cold Front
A cold front forms when cold air moves into an area occupied
by warmer air. The affected area experiences thunderstorms if
the warm air is unstable.
• Occasionally, the flow of air on either side of a
front is neither toward the cold air mass nor
toward the warm air mass, but almost parallel to
the line of the front. In such cases, the surface
position of the front does not move, and a
stationary front forms.
Air flow on either side of the front is neither toward the
cold air mass or toward the warm air mass.
Have blue triangles on one side and red semicircles on
the other of a weather map.
Have gentle to moderate precipitation.
• When an active cold front overtakes a warm
front, an occluded front forms.
Formation of an Occluded Front
An occluded front forms
when a cold front
overtakes a warm front,
producing a complex
Middle-latitude cyclones are large centers
of low pressure that generally travel from
west to east and cause stormy weather.
Satellite View of a Mature Cyclone
Middle-Latitude Cyclone Model
Air Flow Aloft
More often than not, air high up in the
atmosphere fuels a middle-latitude cyclone.
Movements of Air High in the Atmosphere
Movements of air high in the atmosphere fuel the cyclones
and anticyclones near Earth’s surface.
Fronts Foldable (page 55)
Create a four-door foldable with the four
main fronts that affect our weather.
•Name of the Front (outside)
•Description of each type;How it forms;
Weather Associated with; (inside)
•Drawing of Front Type with Symbols
(inside) Use correct color
Post Test (p. 114)
1. What is a middle latitude cyclone?
2. What is the role of air flow aloft?
3. Compare and contrast warm fronts
and cold fronts