Transcript Hurricanes, Thunderstorms, and Tornadoes

Severe Weather
Hurricanes, Thunderstorms, and
Tornadoes
Ingredients for a storm…
• Heat From the Sun
• Differences in Air Pressure
• Water
What is a hurricane?
• A hurricane is a large, swirling, lowpressure system that forms over the warm
Atlantic Ocean.
Hurricanes form over warm ocean
water.
• Near the equator, warm ocean water
provides the energy that can turn a
low pressure center into a violent
storm.
• As water evaporates from the ocean,
energy moves from the ocean water
to the air. This energy makes warm
air rise faster.
• Tall clouds and strong winds develop.
• As winds blow across the water from
different directions into the low, the
Coriolis Effect bends their path into a
spiral.
• The winds blow faster and faster,
around the low, which becomes the
center of a storm system.
Parts of a Hurricane
Parts of a Hurricane
• Eye - The calm, center of the hurricane.
• Eyewall - The wall of dense thunderclouds
surrounding the eye. The strongest winds of
the hurricane are in the eyewall.
• Spiral Rainbands - A series of long,
spiraling bands of rain clouds in a hurricane.
What things make hurricanes loose
strength?
• 1. Crumple a piece of paper, then flatten it out.
Crumple and flatten it out again.
• 2. Spin the top on the flattened paper.
• 3. Spin the top on a smooth surface. Count the
seconds until it stops spinning.
What do you think?
How does the texture of the surface
affect the rate at which the top looses
energy?
Why do hurricanes seem to die
over land?
• As long as a hurricane is over
water, the warm, moist air rises
and provides energy for the
storm.
• When a hurricane reaches land,
however, its supply of energy
disappears and the storm loses
power.
Create a Model of a Hurricane!
• Using glue, blue construction paper, and
cotton balls, create a model of a hurricane,
labeling and explaining each part.
• You may use your graphic organizer for
assistance!
Tornadoes
•Tornadoes form from severe
thunderstorms. They are very
destructive because they have
a high energy density. They
also don't last very long. This
makes it hard to learn about
them. Since scientists don't
know much about tornadoes,
it's also hard to forecast them
Tornadoes
• The fastest
recorded wind
speed is 230 miles
per hour and
occurred in New
Hampshire in 1934.
Although, winds
can get faster in
tornadoes. The
windiest place in
the world is in
Antarctica.
• In severe thunderstorms, wind
at different heights blows in
different directions and at
different speeds.
• This difference in wind speed
and direction, called wind
shear, creates a rotating
column parallel to the ground.
• A thunderstorm’s
updraft can tilt the
rotating column
upward into the
thunderstorm
creating a funnel
cloud.
• If the funnel comes
into contact with
Earth’s surface, it is
called a tornado.
Tornado Alley
• This map shows where most tornadoes
form in the United States. The red area
is known as "Tornado Alley".
• Warm moist air from the Gulf of Mexico
collides with
• Cold dry air.
Thunderstorms
• It is late afternoon. The white puffy clouds
that have been growing all day are
replaced by a greenish sky. A distant
rumble is heard...then another. It starts to
rain. A flash of light streaks the sky,
followed by a huge BOOM. Welcome to a
thunderstorm.
Thunderstorms
Thunderstorms
are small, intense
weather systems
that produce
strong winds,
heavy rain,
lightning, and
thunder.
When do thunderstorms occur?
• Thunderstorms form from warm moist
air and along cold fronts.
How are thunderstorms
created?
• There are three ingredients for
thunderstorms to form:
• 1. The air near the earth’s surface must be
warm and moist. It rises or moves upward,
which is called an updraft.
• 2. The atmosphere must be unstable- the
surrounding air is colder than the rising air
mass. As the warm air mass rises, it cools
and turns into water vapor, condenses and
forms CUMULONIMBUS Clouds.
Vertical Air Movement
3. As the cloud
continues to build, ice
particles form near
the top of the cloud.
As they get large-they
form H-A-I-L. As the
ice particles or H-A-IL falls, cold air moves
down with it, causing
a downdraft.
Let’s Investigate!
• How do updrafts form???
• Draw and describe what
happens.
• In what ways is this
demonstration of water similar to
warm air in a thunderstorm?
• Challenge: How could you
create a downdraft in this
experiment?
Three Stages of a
Thunderstorm
Create a Foldable on Stages of a
Thunderstorm.
Turn to page 589 in the text book.
Draw, Label, and Explain the stages of a
thunderstorm.