Severe Weather
and Storms
◦ Storms:
◦ Violent disturbances within the atmosphere.
◦ Caused by sudden changes in air pressure which
cause rapid air movement in an area.
◦ Similar conditions often produce different types of
storms.
Thunderstorms
◦ A thunderstorm is a small storm often accompanied by heavy precipitation and
frequent thunder and lightning.
◦ Form in large cumulonimbus clouds (also called thunderheads) on hot, humid
afternoons
Thunderstorms
◦ Warm, humid air rises rapidly
and the air cools, forming
dense thunderhead clouds
◦ Heavy rain falls, sometimes
along with hail
◦ Within the thunderhead
cloud there are strong
updrafts and downdrafts
Lightning
◦ Lightning is a sudden spark, or electrical discharge
◦ Positive and negative charges jump between parts of a cloud, or
between nearby clouds, or between a cloud and the ground
Thunderstorms
◦ Lightning heats the air to 30,000oC
◦ Thunder is the sound of the rapidly heated air
expanding suddenly and explosively
◦ Light travels faster than sound so you see lightning
before you hear thunder
Lightning Strikes in the U.S.
◦ This map shows how often lightning strikes different
parts of the lower 48 states. Central Florida has the
most intense concentration of cloud-to-ground
lightning because it has a lot of warm, humid air. The
Pacific Northwest has almost no lightning.
Thunderstorm Safety
◦ Go INSIDE!
◦ Do NOT touch
anything that can
conduct electricityespecially metal
objects and bodies
of water
◦ Crouch down in a
low area-avoid trees
Tornadoes
◦ A tornado is a rapidly whirling, funnel-shaped cloud that
reaches down from a storm cloud to touch Earth’s
surface
Tornado Formation
◦ Warm, moist air flows in at the bottom of a
cumulonimbus cloud and moves upward
◦ A low pressure area forms inside the cloud
◦ Warm air rotates as it meets winds blowing in different
directions at different altitudes
◦ Tornado Alley is an area of the United States that has a
high frequency of tornadoes because cold, dry air moves
south from Canada to meet warm, humid air from the
Gulf of Mexico
◦ 5 states that cross Tornado Alley are:
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Texas
Oklahoma
Kansas
Nebraska
Iowa
The Fujita Tornado Damage Scale
◦ Tornadoes are ranked on the Enhanced Fujita scale by the
amount of damage they cause.
Tornado Safety
◦ A tornado watch is an announcement that tornadoes
are possible in your area. Stay tuned to the radio or
television news.
◦ A tornado warning is an announcement that a tornado
has been sighted. Take shelter immediately!
◦ The safest place to be during a tornado is in a storm
shelter or the basement of a well-built building
◦ If you cannot get underground, go the center of the
lower level and stay away from windows and doors.
Hurricanes
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A hurricane is a tropical cyclone that has winds of 119 km/h or higher
Hurricanes form in the Atlantic, Pacific, and Indian Oceans
In the western Pacific Ocean, hurricanes are called typhoons
A hurricane begins over warm ocean water as a low-pressure area, or
tropical disturbance.
A hurricane draws its energy from the warm, humid air at the ocean’s
surface
As the air rises and forms clouds, more air is drawn into the system
Inside the storm are bands of very high winds and heavy rains
Winds spiral inward toward the area of lowest pressure at the center
Hurricane Names
◦ Hurricanes are given names to help us identify them and
track them as they move across the ocean
◦ Men and women's names are used
◦ One name for each letter of the alphabet except Q, U, and
Z
◦ World Meteorological Organization uses six lists in
rotation
◦ The only time a new name is added is if a hurricane is
very deadly or costly
◦ If that happens then the name is retired and a new name
is chosen.
Hurricane Formation
Hurricanes
◦ Hurricanes last longer than other storms, usually a week or more.
◦ After a hurricane passes over land, it no longer has warm, moist air to
draw energy from so it loses strength.
◦ A storm surge is a “dome” of water that sweeps across the coast
where a hurricane lands.
◦ For safety during a hurricane, people are told to evacuate.
◦ Evacuate means to leave the area immediately.
Tornado Alley Worksheet
◦ Worksheet and map
◦ Worst Tornados in History
◦ Tornado Rampage 2011
◦ Find some type of hurricane activity and add here
Culture- Myths
◦ In the past, people from many cultures interpreted the
weather as signs from the gods. Angry gods might send
lightning to strike a person or place.
◦ Some Native Americans believe that giant birds called
thunderbirds beat their wings to produce thunder. The
flashing of their eyes creates lightning.
◦ An ancient Chinese myth tells how a thunderstorm is created
by different gods. The thunder god is helped by Mother
Lightning. She produces lightning using mirrors in her hands.
The Master of the Rain sprinkles water from his pot with a
sword. The Little Boy of the Clouds, piles up the clouds, while
the Prince of Wind releases winds from a bag.
◦ According to Kenyan legend, God creates two rainbows,
one male and one female, which must work together to
stop the rain.
It's raining cats and dogs
◦ According to the Library of Congress, the true origin of the phrase is
unknown. Some popular ideas about the origin of the phrase
include references to Norse and Greek mythology.
◦ Witches, which were associated with black cats, and the Norse god
of storms, which was associated with dogs, may have been an early
reference to storms. dogs" may refer to a storm with wind (dogs)
and heavy rain (cats).
◦ Cata doxa, a Greek expression meaning "contrary to experience or
belief" may have meant it is raining unusually hard.
Weather Folklore
◦ Red sky at night, sailors delight; red sky in morning, sailors take warning. What does that
mean?
◦ Winter weather folklore forecasting
◦ Weather Folklore Activity Sheet and poems
Create your own myth
◦ Example - The Vikings believed thunder was caused by Thor. In
Norse mythology, Thor was the god of thunder. He produces
thunder with his hammer, called Mjolnir, which means "The
Destroyer". This hammer was made by dwarfs, and would
magically return to Thor's hand whenever he needed it.
◦ Create an original weather myth to explain some aspect of
weather in words and in pictures.
Video and Questions
◦ United Streaming:
Hurricanes, Tornadoes and Thunderstorms – 24min.
◦ Video Questions and answers
Characteristics of Weather
◦ Organize the characteristics into categories.
◦ Write down an explanation of how you organized the characteristics and why you
categorized them that way.
◦ Share your categories and explanation with the class.