severe weather!!!!!!! chapter 20.3
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Severe Weather!!!!!!! Chapter 20.3. What is severe weather?. Weather that poses a danger. What is a thunderstorm?. A storm that produces: 1. Lightning 2. Thunder 3. Heavy Rain and/or flooding 4. Strong winds and possibly hail - PowerPoint PPT PresentationTRANSCRIPT
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What is severe weather?
Weather that poses a danger.
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Mr. Fetch’s Earth Science Classroom
What is a thunderstorm?A storm that produces: 1. Lightning
2. Thunder 3. Heavy Rain and/or flooding
4. Strong winds and possibly hail
They last about 15-60 minutes.
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Mr. Fetch’s Earth Science Classroom
How do thunderstorms form? When warm, moist air is lifted up violently.
The air rises up to form a cumulonimbus cloud.
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If the winds are over 58 mph, the thunderstorm is said to be a SEVERE THUNDERSTORM.
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How does lightning form?
Updrafts and downdrafts of wind and rain
cause different parts
of a cloud to become
electrically charged.
- (+) charge at top of cloud
- (-) charge at bottom of cloud
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•Every second between a lightning flash and thunder means the storm is 1 mile away.
Speed of Light: 186,000 miles/second or 300,000 km/second
Speed-of-sound: 1100 ft/sec (330 m/sec)
How Far Away is Lightning?
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The odds of becoming a lightning victim in the U.S. in any one year is 1 in 700,000.
The odds of being struck in your lifetime is 1 in 3,000.
Man Struck by Lightning
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Talking on the telephone is the leading cause of lightning injuries inside the home
Standing under a tall tree is one of the most dangerous places to take shelter outside
Is Your Car Safe Video?
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Lightning Facts
NO SUCH THING AS HEAT
LIGHTNING = FAR AWAY
THUNDERSTORM
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Thunder Caused by the rapid expansion and
contraction of the air surrounding a lightning bolt.
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Tornado: A rotating column of air.
1. Wind shear causes air to rotate.2. The rotating column of air is lifted by updrafts3. The column of air touches the ground = tornado
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How are tornados classified?
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3 out of every 4 tornadoes in the world happen in the United States
A Tornado in Oklahoma once destroyed a whole motel. People later found the motel’s sign in Arkansas
The United States have an average of 800 tornadoes every year
The chances that a tornado is a F5, the highest classification for a tornado on the F-scale, is less than 0.1%
A Tornado can occur at any time, but most often between 3pm and 9pm
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Storm Chasing - your future career?http://www.youtube.com/watch?
v=bhGWWY1nCWw&feature=relmfu
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Hurricanes
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http://www.cbsnews.com/htdocs/natural_disasters/hurricanes/framesource_flash.html
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Low Pressure Systems Associated with hurricanes
Strong winds and bad weather Move Counterclockwise
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5 Things a Hurricane needs to Form
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Progression to a Hurricane
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Saffir-Simpson Scale is used to measure a hurricane’s intensity
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Most dangerous part of hurricanesStorm SurgeStorm Surge – like what – like what happened with Hurricane happened with Hurricane Katrina Katrina
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An abnormal warming of surface water ocean waters in the Eastern Tropical Pacific.
Occurs every 2 - 9 years or so….
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• Droughts in Australia, Indonesia, Pacific NW of US. • Heavy storms resulting in flooding in California,
Midwest US and Central Europe and Asia.
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Happens when the eastern Pacific is unusually cold after being unusually hot for years.