2. What are
fronts ?

3. Air Masses
• a body of air extending hundreds or thousands of miles sideways and
sometimes as high as the stratosphere and having nearly the same
conditions of temperature and humidity.

4. Types of air masses
Humid Air masses
Dry Air masses

5. Air Fronts
• When air masses move across the surface of the
earth they may collide.
• These collisions happen halfway between one of
the poles and the equator.
• The 2 air masses don’t mix much when they
collide.
• Each keeps its own temperature ,humidity and
pressure.
• As a result ,a boundary forms, this boundary is
called “Front”.

6. Types of Air Fronts
Scientists classify fronts by the characteristics and movements
of the two air masses.

7. 1-Warm Front
When a warm air mass moves into an area of
cooler air ,the boundary between the air is
called
“Warm front”
The warmer ,less dense air slides up over the
cooler denser air in a wide ,gentle slope

8. • As the warmer air cools ,its relative humidity
increases, and the water vapor condenses into
clouds.
• A warm front usually results in steady rain .

9. 2)Colda cold air mass moves into an area of
Front
• When
warmer air , the boundary between air masses is
called “Cold front”
• The colder ,denser air slides under the warmer
air is pushed up .

10. • As the warmer air cools ,the water vapor
condenses and form clouds that brings
precipitation

12. 3)Occluded front
This produces a wedge of warm air between 2
masses of cold air .The formation of an
occluded front often indicates that a storm will
happen but will not last for long.