severe storms
DESCRIPTION
Severe Storms. Thunderstorms. Occur in warm, moist air masses and along fronts. Sinking rain, cooled air, and strong updrafts of warm air cause strong winds. If winds reach 89 km/h or faster, it is a severe thunderstorm. Flash floods, strong winds, hail. Thunderstorms. Lightning. - PowerPoint PPT PresentationTRANSCRIPT
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Severe Storms
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Thunderstorms• Occur in warm, moist air masses
and along fronts.• Sinking rain, cooled air, and strong
updrafts of warm air cause strong winds.
• If winds reach 89 km/h or faster, it is a severe thunderstorm.
• Flash floods, strong winds, hail.
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Thunderstorms
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Lightning• In a storm cloud, warm air is lifted rapidly as
cooler air sinks. This movement causes different parts of the cloud to become oppositely charged.
• When the current flows between opposite charges, lightning flashes.
• Occurs in 3 places: within a cloud, between clouds, cloud and the ground.
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Lightning
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Thunder• Results from rapid heating of air around
lightning. (Lightning is 30,000 degrees celsius.. 5x the surface of the sun!!)
• The extreme heat causes air around the lightning to expand rapidly. Then it cools and contracts.
• The rapid movement of molecules forms sound waves heard as thunder.
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Thunder
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Tornadoes• A violently rotating column of air in contact
with the ground.• In severe thunderstorms, wind at different
levels blow at different direction and speed. This is called wind shear.
• Rips apart building, uproot trees, blow through glass. Can lift animals, cars and houses in the air.
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Tornadoes
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Hurricanes • Large, swirling, low pressure system
that forms over the Atlantic Ocean.• Must have winds of at least 119
km/h.• Category 1-5 (250 km/h)
• Typhoon- forms over the Pacific Ocean.
• Cyclones- Form over the Indian Ocean.
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Hurricanes
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Images from Space
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Strongest Hurricanes
• Begin as low pressure systems west of Africa.• Steered by surface winds.• travel west.• Gains strength from heat + moisture of warm
ocean water. • When it hits land, it loses power and dumps
water.• Strongest winds are within 80 km of the eye.
(50 miles)
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Blizzards• Winds at 56 km/h• Blowing snow• Visibility less than 400m• These conditions must persist for 3
hours or more.
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Blizzards
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National Weather Service
• watch- conditions are favorable• warning- weather exist, take cover!