Transcript Fronts and Pressure Systems

Fronts and Pressure
Systems
Review
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What is an air mass?
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a large volume of air in which temperature and
humidity are nearly the same in different locations
over a large area .
What happens when
air masses meet?
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Weather can change.
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New air moving into an area brings different
weather.
Fronts
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A front is a boundary between two air masses.
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As one air mass pushes another, warm air at the
boundary will be pushed upwards.
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This forms clouds.
So it forms clouds…
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Often weather will become cloudy or stormy
when a front passes.
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Once the front has passed you will experience
the temperature and humidity of the new air
mass.
How do I know which one it is?
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The names tell you which way the temperature
will change and which type of front it is.
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Colder air comes with a cold front.
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Warmer air comes with a warm front.
Cold Fronts
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When cold air moves into an area of warmer air
you have a cold front.
Move quickly.
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Has a steep front edge.
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Warm air rises steeply and quickly. Forms
Cumulonimbus Clouds
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Cold Front
Rising Air
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Quickly rising warm air cools and water vapor
condenses on condensation nuclei producing tall
cumulonimbus clouds and usually precipitation.
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After the storm the air is usually cooler and very
clear.
Example
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What would the weather be like if a cold front
moved into Muncy today?
And on a weather map…
The blue triangles represent a cold front.
Review
Explain a cold front.
 How air rises?
 What cloud type forms?
 What type of weather follows?
 What do we use to show a cold front on a
map?
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Warm Fronts
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When warm air moves into an area of cooler air you
have a warm front.
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Moves slowly.
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Air rises slowly.
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Warm air moves up and over the mass of colder
air.
Clouds
Warm air rises slowly and water vapor
condenses forming clouds.
 There are a series of cloud types as warm
fronts approach.
 1st – cirrus
 2nd – altocumulus or altostratus
 3rd – stratus / nimbostratus
 Brings hours of steady rain or snow.
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Warm Front
On a weather map…
Red semicircles represent a warm front.
Review
High and Low Pressure
Anticyclone – location
with highest pressure
Cyclone – location
with the lowest
pressure
Pressure
High pressure rotates
clockwise and outward
as air moves to areas of
low pressure.
Low preesure rotates
counterclockwise and
inward then lifts
upward.
Low Pressure System
High Pressure System
On a weather map…
Activity
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When you are done with the power point notes
open the following link and complete
“Precipitation Along Fronts” scaffolding
activity.
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http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr
clm/act/fpr.rxml
Activity 2
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When you are done with the power point notes
open the following link and complete
“Pressure” scaffolding activity and complete all
work 1-5.
http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr
clm/act/prs.rxml
Activity 3

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When you are done with the power point notes
open the following link and complete
“Midlatitude Cyclone” scaffolding activity and
complete questions 1-5.
http://ww2010.atmos.uiuc.edu/(Gh)/guides/cr
clm/act/cyc.rxml