Transcript Severe Weather

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Thunderstorms are small, intense weather
systems.
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Strong winds
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Heavy rain
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Lightning and thunder
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Occur along cold fronts
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In order for thunderstorms to occur:
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The air near the Earth’s surface must be warm and
moist.
The atmosphere must be unstable (warm air that
rises rapidly).
Lightning and thunder
Lightning is a large electrical discharge between two
oppositely charged surfaces.
 Thunder is the sound that results from the rapid
expansion of air along the lightning strike.
 Lightning Video Clip
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A tornado is a small, rotating column of air.
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Forms during thunderstorms.
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High wind speeds
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Center of a tornado is called a vortex.
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75 % of a all tornadoes occur in the U.S.
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U.S. averages about 1,000 per year
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Wind travels in two different directions.
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Air between begins to roll.
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The “roll” turns vertically and begins to rotate
because of the updrafts.
Turns into a funnel and touches the ground.
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Waterspouts are tornadoes that form over
water.
Tornado Alley – an area east of the Rocky
Mountains. It is mainly in Texas, Oklahoma,
and Kansas that experiences the highest
number of tornadoes per year.
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Why? Cool dry air (north) meets warm moist air
(south).
BrainPop- Tornados
F-0
F-1
F-2
F-3
F-4
F-5
40-72 mph, chimney damage, tree branches broken
73-112 mph, mobile homes pushed off foundation or
overturned
113-157 mph, considerable damage, mobile homes
demolished, trees uprooted
158-205 mph, roofs and walls torn down, trains overturned,
cars thrown
207-260 mph, well-constructed walls leveled
261-318 mph, homes lifted off foundation and carried
considerable distances, autos thrown as far as 100 meters
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Hurricanes are counterclockwise spinning
storms with winds ≥ 74 mph.
The intensity of a hurricane is measured using
the Saffir-Simpson Scale.
Ingredients needed for a hurricane to form:
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Water temperature 80°F or more.
Surface level low pressure
Upper level high pressure.
BrainPop- Hurricanes