Air Masses and Weather Fronts
Study Guide Notes
The study of weather is
meteorology
• Someone who studies weather is
called a meteorologist
Air Pressure and Weather
• High Pressure = air is sinking
sunny because the air pushes down
allowing no evaporation = no clouds
• Low Pressure = air is rising
rainy and stormy because air rises up
allowing for lots of evaporation = lots of
clouds and rain
• An AIR MASS is a body of air with a certain
temperature and moisture level. Caused by
where it formed.
C = Continental: the air came from over the land = air is DRY
M = Maritime: the air came from over the ocean = air is WET
P = Polar: the air came from near the poles = air is COLD
T = Tropical: the air came from near the equator = air is HOT
Movement of Air Mass
• 1. Air masses are moved around by global winds.
The global winds above the U.S. always blow
Northeast.
• 2. Air masses are also pushed around by the
Jet Stream
– Jet Stream= (fast moving stream of air over US)
changes it’s pattern of movement each day.
The movement of weather
and air masses depends on
Both of these factors.
Fronts
• When two air masses meet, the air within
them doesn’t mix. The air masses fight!
• often resulting in rain and storms.
• At all fronts, warmer air gets pushed up
Causing low pressure and clouds/rain.
–4 Types of Fronts:
1.Warm
2.Cold
3.Occluded
4.Stationary
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•
•
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Warm Fronts
The area was cold, then warm air moved in to that area.
Warm air is forced upwards as it hits colder air.
Rises up to make clouds and light rain.
After front passes it warms up.
Cold Fronts
• The area was warm, then cold air moves in to that area.
• The cold air coming in, forces the warm air to rise up
fast (then it cools into clouds)
• Causes lots of violent storms (thunderstorms and
heavy rain)
• After front passes temperature is cooler
Occluded Fronts
• When a cold front (moving quickly) catches up to a
warm front (moving slowly)
• Warm air is trapped between two bodies of cold air.
• Long periods of light rain.
• Colder after front passes.
Stationary Fronts
• Warm and cold front run into each other.
• These fronts are stationary (don’t move) because
they sit still for many days with light rain.
3-Day Forecast for Chicago
Today
Because:
Tomorrow
Next Day
Quiz 1
Describe the weather in Chicago right
now and how it will change over the
next 2 days. Why?
Chicago
3-Day Forecast for Reno
Today
Because:
Tomorrow
Next Day
Quiz 2:
Describe the weather in Reno right
now and how it will change over the
next 2 days. Explain why.
Reno