Download Name: Core: ____ Date: THUNDERSTORMS, HURRICANES

Name: ________________________________
Core: ____
Date: ______________
THUNDERSTORMS, HURRICANES, TORNADOES, AND WINTER STORMS – September 8, 2015
STORMS = natural disturbances in the atmosphere that involve air pressure, clouds, precipitation, and strong winds.
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Each type has its own characteristics and dangers.
THUNDERSTORMS = brief, intense electrical storms that affect a small area.
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Thunderstorms occur when warm, humid air rapidly rises to create strong updrafts.
As the air cools, it condenses into tall cumulonimbus clouds (thunderheads).
Characterized by lightning and thunder, strong winds, heavy rain and sometimes snow, hail or no precipitation
at all.
LIGHTNING
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When the ground is hot, it heats the air above it. This warm air rises. As the air rises, water vapor cools and
forms a cloud. When air continues to rise, the cloud gets bigger and bigger. In the tops of the clouds the water
vapor turns to ice.
These small bits of ice bump into each other as they move around and build up electrical charges.
Lighter, positively charged particles form at the top of the cloud & heavier, negatively charged particles sink to
the bottom of the cloud.
When the positive and negative charges grow large enough, a giant spark – lightning – occurs between the two
charges within the cloud. This is like a static electricity spark, but much bigger!
THUNDER
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Lightning heats the air so that it expands explosively. The loud clap is thunder.
Light waves travel faster than sound waves, so a thunderclap may come many seconds after the lightning is
spotted.
HURRICANES = huge, rotating storms that form over the ocean near the equator.
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Characterized as having strong winds, heavy rains (flooding), large, powerful waves (storm surge) and tornadoes.
How do hurricanes form?
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Form in the tropical latitudes (10o - 25oN) in summer and autumn when sea surface temperature is 82oF or
higher.
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Warm, humid air over the ocean rises and creates a low pressure cell called a tropical depression with
thunderstorms around it.
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Air begins to rotate around the low pressure center
-Counterclockwise in the Northern Hemisphere
-Clockwise in the Southern Hemisphere
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As more air rises, water vapor continues to condense, releasing energy from latent heat…and the storm gets
stronger.
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The tropical storm may then build into a hurricane in 2-3 days.
The Eye of the Hurricane
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At the center of a hurricane is a small area where the air is calm and clear. This is the eye of the hurricane.
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The eye forms at the low-pressure center of the hurricane where air is rising upward.
How do hurricanes move?
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Hurricanes originate in the trade winds and move to the west in the Northern Hemisphere.
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When they reach the westerlies, they switch direction and travel toward the north or northeast.
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May cover 500 miles in one day!!
How are hurricanes classified? 1 = weak
2 = moderate
3 = strong
4 = very strong
5 = devastating
TORNADOES = violently whirling wind sometimes visible as a funnel-shaped cloud.
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Produced from severe thunderstorms
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Spiraling high winds
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Extremely low pressure
What causes tornadoes?
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Updrafts and downdrafts in the thunderstorm (caused by the unstable air) interact with the wind shear.
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Spinning air around the cyclone converges inward toward the thunderstorm, causing it to spin faster.
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Exists only ahead of a cold front and a low pressure system.
FLOODS = occurs when an area is inundated (deeply covered) with water.
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Commonly associated with hurricanes and thunderstorms
WINTER STORMS are associated with quickly moving cold fronts; includes blizzards and ice storms.
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High winds
Very low temperatures
Large accumulations of snow