Transcript Thunderstorms & Tornados:

Thunderstorms
:
Aim: What are the
ingredients of a
thunderstorm?
Describe all of the events you
see, feel and hear during a
storm.
What is a storm?
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A storm is a severe
disturbance in the
atmosphere.
Types of storms include:
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Thunderstorms
Tornados
Hurricanes
How is a thunderstorm
formed?
A cold air mass runs
into a warmer air
mass and pushes the
warm air up rapidly.
Thunderstorms occur
along cold fronts.
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Cumulonimbus clouds form, dropping heavy rain
Storm front (cold front) –
where air masses with very
different properties collide
How does lightning form?
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Lightning is created when
negative charges in the bottom of
clouds are attracted to the
positive charges on the ground
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Lightning and Thunder
Lightning animation
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What is thunder?
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Thunder is the rapid expansion of air
molecules that happens when lightening
rapidly heats the air around it.
Thunder always accompanies lightning
because it is the lightning that causes it.
Thunder animation
What else can form in a thunderstorm?
How does hail
form?
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Hail is formed when updrafts in a thundercloud carry
raindrops upwards into extremely cold areas of the
atmosphere where they freeze into lumps of ice.
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The lumps fall to earth at very high speeds (up to
120 miles per hour).
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The largest hailstone ever recorded measured over
5.6” in diameter and weighed almost 2 pounds
(Ouch!).
How does hail form?
See A thunderstorm!
Observe an animation of a thunderstorm.
Summary: What are the
ingredients of a thunderstorm?
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Cold Air mass
Warm Air mass
Cold front
Moisture in the air
Lightning
Thunder
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Cumulonimbus
clouds
Hail
Tornados
Why is their hair standing on end?
Thunderstorm Safety
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Read the article and answer the following
questions:
Where is the best protection from a
thunderstorm?
If outside, where should you go?
If in a group, what should you do?
If you feel your hair stand up…what should
you do?
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25 million cloud-to-ground lightning strikes
occur in the U.S. each year
The air within a lightning strike can reach
50,000 degrees Fahrenheit
Lightning heats its path 5 times hotter than
the surface of the sun
One ground lightning stroke can generate
between 100 million and 1 billion volts of
electricity
Lightning safety
Don’t touch metal objects
(they conduct electricity).
Find a low area –
make yourself as small as
possible
Stay away from other tall
things – like trees and
telephone poles
Spread out from a group
Tornados
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A rapidly whirling, funnel
shaped cloud that
reaches the ground
VERY strong, fast winds
Form from thunderhead
clouds called
“super cells”
“Tornado alley” is in the
Great Plains – more
tornados than any other
place in world

http://www.classzone.com/books/earth_scien
ce/terc/content/visualizations/es2006/es2006
page01.cfm?chapter_no=visualization
Tornados
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Tornado watch – means they are possible
Tornado warning – its been spotted on ground
Safety - Best place to be is in a basement
Little flooding threat
Unpredictable – form from thunderstorms
Narrow path of destruction
Fast moving
Often in spring – when the seasons are changing
Hurricanes
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Travels NW to NE
steered by
prevailing winds
June – November
Evacuations may be
necessary near
coast because of
storm surge.
Go to interior room
away from windows
Hurricanes
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Starts as a tropical
depression (low
pressure), then tropical
storm
Very low pressure in the
eye – most dangerous
winds are in the NE half of
the eye wall.
Maritime tropical air mass
Loses its energy as it is
farther from warm water
Most damage done by
storm surge (flooding)
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http://www.classzone.c
om/books/earth_scienc
e/terc/content/visualizat
ions/es2008/es2008pa
ge01.cfm?chapter_no=
visualization
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http://www.brainpop.co
m/science/weather/hurri
canes/