Understanding Fronts

Air Mass Review
► An
air mass is a defined as a large body of
air with very similar characteristics.
► Generally speaking, air masses are generally
defined by temperature and humidity
► Air masses are named based on the source
Types of Air Masses
Continental Polar (cP), “cold and dry”
 Originates closer to the Poles over
land-locked regions. Not as cold as
Arctic air masses. Forms farther to the
south than Arctic air, more common.
Central and northern Canada and
Continental Tropical (cT), “hot and
 Originates closer to the Tropics over
land-locked regions. Usually forms
over the Desert Southwest and
northern Mexico.
Maritime Polar (mP), “cool and moist”
 Originates closer to the Poles over
water. Usually brings cloudy, damp
weather, not as cold as continental air.
Maritime Tropical (mT), “warm and
 Originates over warm tropical waters
of the Southern Atlantic and the Gulf
of Mexico. Responsible for hot, humid
days of summer across the South and
“Blue Ice Weather”
In your spiral notebook on the next available LEFT HAND SIDE PAGE, predict
what you think will happen when you add the blue ice cube and red food
coloring to water in the plastic container?
1. Fill the plastic box two-thirds full with water at room temperature.
2. Wait until the water is completely still before doing step 3
3. Carefully drop a blue ice cube into the water at one end
4. Carefully drop three or four drops of red food coloring at the other end
5. Watch what happens!
Describe what happened in your science spiral underneath your hypothesis.
Write a conclusion in your spiral notebook underneath the results.
Why do you think this happened?
How do you think this is related to air masses and/or weather?
Understanding Air
Masses & Fronts
Sometimes two air masses with different temperatures and
humidity bump into each other….
When this happens a FRONT is formed!
Front – boundary where unlike air masses meet, but do not mix.
There are 4 types: cold, warm, stationary and occluded. The kind of front that
develops depends on the characteristics of the air masses and how they are
Types of Fronts
 A fast-moving cold air mass
overtakes a warm air mass
 A warm air mass overtakes a
slow-moving cold air mass.
 Cold and warm air masses
meet, but neither can move the
 A warm air mass is caught
between two cooler air masses.
Cold Front
Cold Front
► Marked
on a map with a blue line and blue
triangles pointing towards the warm air.
► Associated
with cumulus & cumulonimbus
clouds ahead of the front in the warm air,
producing showers and thunderstorms.
Warm Front
Warm Front
► Marked
on a map by a red line with red
semi-circles pointed towards the cool air (in
the direction the warm air is retreating to.)
► Generally associated with stratus type
clouds, overcast skies, fog, and general rain
or snow.
Stationary Front
► Marked
by alternating blue lines & blue
triangles (pointed in the direction of the
warmer air) and red lines & red semi-circles
(pointed in the direction of the cooler air)
► Water vapor in the air condenses into rain,
snow, fog or clouds. If it remains over an
area it may bring days of clouds and
precipitation. http://www.phschool.com/atschool/phsciex
Occluded Front
► Marked
by a purple line with alternating
purple triangles and purple semi-circles, all
pointing in the direction of the frontal
► The weather may turn cloudy and rain or
snow may fall
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