Download Hurricane - Cabarrus County Schools

Storms
Storms
• A storm is a violent disturbance in the atmosphere
• 4 major types of storms:
– Thunderstorms
– Tornadoes
– Hurricanes
– Winter Storms
• A meteorologist is a scientist who studies weather
and tries to predict it
Thunderstorms
How Thunderstorms Form
• For a thunderstorm to form, three conditions
must exist.
1. There must be an abundant source of moisture
in the lower levels of the atmosphere.
2. Some mechanism must lift the air so that the
moisture can condense and release latent heat.
3. The portion of the atmosphere through which
the cloud grows must be unstable.
Thunderstorms
 Thunderstorms happen
when a cold front
meets a warm front,
and a cumulonimbus
cloud forms
 The air near the Earth’s
surface must be warm
and moist
 The atmosphere must
be unstable
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
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
 Lightning can be over 50,000 degrees F
 Record for being hit by lightning—7 times!
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
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.
Calculating Lightning Distances
• Watch the sky for a flash of lightning.
• Count the number of seconds until you hear thunder.
• Divide the number of seconds by 5 to calculate the
distance the storm is away from your location in
miles (or divide by 3 for kilometers).
• Ex: If you counted 18 seconds from when you saw the
lightning, the strike was 3.6 miles (6 kilometers) from your
location.
Divide Number of Seconds
by 3 for Distance in Km
or 5 for Distance in Miles.
 Hail is only produced by
cumulonimbus clouds
Hail
◦ Water in the cloud freezes onto
dust or dirt
◦ The ice ball falls in the cloud, gets
blown back up, and gathers more
ice
 Ice forms in layers in hail, like an onion
◦ Eventually, the hail gets too heavy
to get blown around anymore, and
falls to Earth
◦ Hail can be over 6 inches around
and weigh more than a pound!
Safety
 Lightning kills more people
than tornadoes or hurricanes
 Stay away from metal objects
and tall structures
 If you are outside, get down
flat on the ground, and don’t
touch other people
• Lightning can jump from one
person to another
Tornadoes!
Tornadoes
• Violent low pressure windstorms that take the
form of a vortex.
• Vortex- spinning/rotating, often turbulent,
column of air
• The vortex extends downward from a
cumulonimbus cloud – produce rain and hail
• Move counterclockwise
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
How a tornado occurs:
Tornado formation:
• Wind starts traveling in
2 different directions
• This causes a layer of air
in the middle to rotate
like a toilet paper roll
How a tornado occurs:
• Finally, when
the funnel
cloud reaches
the ground,
it’s called a
tornado
Where they happen
 Most of the world’s
tornadoes (75%) occur
in the US
– Tornado Alley—The
part of the Plain
States in the US
where tornadoes
are most frequent
• 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:
–
–
–
–
–
Texas
Oklahoma
Kansas
Nebraska
Iowa
Wind Speeds
 Winds can be over
300 mph in a
tornado
 In most cases,
they’re usually
less than 130mph
Tornado Scale
 Tornadoes
are ranked
from F0
(weak) to F5
(very, very
strong)
Tornadoes in North Carolina
•
•
•
•
•
•
Average per year: 16
Average per 10,000 sq. miles: 3.26
Most in One Year: 66 in 1998
Average Tornado Deaths per year: 2
Average Tornado Injuries per year: 39
Deadliest Tornado: February 19, 1884, a
tornado in Anson and Richmond Counties
• killed 23 people.
F4 tornados in NC from 1950
North Carolina has
never had a
recorded F5 tornado
•However, we’ve
had about 27 F4
tornadoes since
1950
•The most recent
F4 was in
Caldwell County
on May 7, 1998
Safety
• There may be
a tornado
when:
– Conditions are
right for a
thunderstorm
– The sky may
be a greenish
color
Safety
• Tornado watch:
Conditions are
right for a
tornado, be
aware
• Tornado warning:
A tornado has
been spotted,
take cover
Safety
How to survive a tornado
• Get in the lowest room of the
house
• Stay away from glass windows or
sharp objects
• Get in a bathtub, and/or under a
mattress
• If you’re outdoors, get in a ditch
– Under a cement overpass will
also work if there’s no ditches,
but it can be dangerous
• The wind acts like a vacuum,
and can suck you out
Fire tornadoes
• Very rarely, the conditions
are right for tornadoes to
form during a fire
– The air forms a vertical
column of air, creating a
fire tornado or “fire whirl”
– Fire tornadoes can topple
trees up to 50 feet tall.
These can also start new
fires during a forest fire
Hurricanes
Definitions
• Hurricane: A large,
rotating tropical weather
system with wind speeds
of at least 70mph
– Can be seen from space
– Creates the most powerful
storms on Earth
– They form in the oceans,
and gain speed in warm
waters
• Over land, they lose energy
and fall apart
Hurricanes
• Whirling tropical cyclones (low
pressure system) producing
winds of at least 119 km per
hour (73 mph)
• US – Hurricanes
• Pacific – Typhoons
• Indian Ocean – Cyclones
• Most powerful storm on Earth
Naming
• Hurricanes are named
alphabetically every year
– Alternate between male
and female names
– Rotate names on a 7 year
basis
– Names for very
destructive hurricanes are
retired and never used
again
• Examples: Hurricanes
Andrew, Hugo, Katrina
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
Formation
• How hurricanes form:
– Warm air above the water
provides energy and
makes clouds
– Wind forces the air
upwards
– Clouds and wind start to
swirl around, creating a
hurricane
Video
Parts of a
Hurricane
Eye: Center of storm,
warmest part, winds
cease, rain ceases
Eye wall: Strongest winds
and rain
Spiral Rain Bands:
extend out from the eye
wall
A Hurricane’s “Death”
• As a hurricane makes landfall,
the supply of warm, moist air
that was fueling it is cut off
• As the downdrafts and rain cool
the land, the strength of the
updraft slows
• Without an updraft, the system
will dissipate, and eventually die
out (just like a thunderstorm)
• This may take days and 100’s of
miles
• Hurricane Ike comes to
Michigan in 2008 (my front yard
in Commerce Township) >
Something to think about
• Because of wind patterns
due to the turning of the
Earth (the Coriolis Effect),
hurricanes spin in opposite
directions in the different
hemispheres
– In the Northern Hemisphere,
hurricanes (and tornadoes!)
spin counterclockwise
– In the Southern Hemisphere,
hurricanes spin clockwise
Scale
• Ranked from:
–
–
–
–
–
–
Tropical depression
Tropical storm
Category 1
Category 2
Category 3
Category 4
Category 5 Strongest
What is Storm Surge Video
Weakest
Locations
• Hurricane season in the
Atlantic Ocean runs from
June 1-November 30th
• In the Atlantic Ocean,
they’re called hurricanes
• In the Pacific Ocean, they
are called typhoons
• In the Indian Ocean,
they’re called cyclones
Hurricanes in North Carolina
• North Carolina has a hurricane make landfall
along the coastline about once every four
years.
– An estimated 17.5% of all North Atlantic
hurricanes have affected our state
– The largest hurricane to ever hit was Hurricane
Hazel in 1954
• Category 4
Hurricane Katrina
• As the storm moved across the
Gulf of Mexico, it RAPIDLY
developed (from a Category II
to a Category V in only 9 hours)
• Wind speeds reached 175 mph
• A mound of water was pushed
toward Louisiana and
Mississippi…
• even though wind speeds
slowed (to a Category III) by the
time it made landfall
The Aftermath
• The most destructive and
costliest natural disaster in the
history of the US
• More than $81 billion dollars in
damage
• More than 1800 people died (700
still listed as missing)
• More than 90,000 square miles
declared a Federal Disaster Area
• More than 3 million people were
left without power
Additional Effects
• There were unforeseen
economic effects
– Gas and Oil production shutdowns
– Unemployment
– Insurance Company
Bankruptcies
– Relocation/Flight from the
region
• Environmental Effects
–
–
–
–
Oil Spills
Erosion
Sewage
Loss of Marine and Animal life
• Looting and Violence
Tropical Storms
Hurricane Hazards
Hurricane Advisories
– The National Hurricane Center, which is responsible
for tracking and forecasting the intensity and motion
of tropical cyclones in the western hemisphere, issues
a hurricane warning at least 24 hours before a
hurricane strikes.
– The center also issues regular advisories that indicate
a storm’s position, strength, and movement.
Tropical Storms
Hurricane Hazards
Hurricane Advisories
How to stay safe during a hurricane
How to stay safe:
• Have an emergency plan figured out
BEFORE the hurricane strikes
• Stay away from low lands that could flood
• Always stay indoors during a hurricane, as
strong winds may blow things around.
• Leave mobile homes and go to a shelter.
• Stay away from downed power lines
• If you get an order to evacuate, then do so
immediately.
Blizzards
Definition
• Blizzard: A severe winter
storm with low temperatures
(under 10 degrees), strong
winds (over 55 mph), and
heavy blowing snow lasting at
least 3 hours
– Most winter snow storms are
NOT blizzards
– Blizzards can occur anywhere
there is snow and high winds
How Blizzards Form
How Blizzards Form:
• Cold, dry Canadian air moves
south and mixes with a warm,
moist air mass moving north
from the Gulf of Mexico
• Blizzards need 3 things to form:
• The air needs to be cold at the
surface
• The atmosphere has to have a lot
of moisture
• There has to be wind to lift the
warm air over the cold air.
Whiteouts
• Whiteouts: A condition that
may happen during a blizzard
where shadows, nearby objects,
landmarks, clouds, and even the
horizon are not visible.
• Land and sky seem to blend
together.
• All you see is white!
• All sense of direction, depth
perception, and even balance may
be lost.
Whiteouts
• Whiteouts happen when
rays of sunlight are
bounced in all directions
between bright white
clouds
• Real whiteouts occur
mostly in the Arctic and
Antarctic during the spring
Effects of Blizzards
• Effects of Blizzards:
– It may be difficult to see or
breathe during a blizzard.
– Traffic accidents
– Cities may shut down as snow
traps people
– Possible death from freezing
temperatures
• The number one cause of death
during a winter storm are heart
attacks while shoveling
Famous Blizzards
• The Blizzard of 1888
• Happened in 1888 in the
Northeastern United States.
• Snowdrifts reached heights of
15 to 50 feet high.
• People were stuck in their
houses for over a week
• 400 people were killed, and 200
ships sunk
Famous Blizzards
• Schoolhouse Blizzard
• Happened in 1888 in the Plain
States
• The day had been calm and
mild, and people left their
homes to enjoy the warmth
• Children got trapped in
schoolhouses, and people got
stranded at work
• Overall, over 500 people were
killed
Famous Blizzards
• The Armistice Day Blizzard:
• Hit New York and surrounding
states in 1940
• Caught many people off guard
with rapid and extreme
temperature change.
• It was 60°F in the morning but
snowing heavily by noon
• Some of those caught unprepared
died by freezing to death in the
snow and some while trapped in
their cars.
• 154 people died
Famous Blizzards
• The Storm of the Century
• Hit the U.S in 1993
• It dropped snow over 26 states
and reached as far north as
Canada and as far south as
Mexico.
• In many southern US states,
more snow fell in this storm than
ever fell in an entire winter.
• At least half of the U.S.
population was affected
• 270 people died and 48 were
reported missing at sea.
Safety
• To stay safe during a blizzard:
• Fill bathtubs with water in case
pipes freeze.
• Make sure windows and doors are
tightly closed and anything movable
in the yard is tied down or brought
inside.
• Bring pets indoors as they may not
survive the cold temperatures
• Stock up on food, especially food
that doesn't need to be prepared
with electricity
• Have batteries for flashlights and
radios.
• Unless it is absolutely necessary,
stay indoors.
Recurring Weather
Floods and Droughts
• Floods can occur when weather patterns cause
even mild storms to persist over the same area.
Droughts are extended periods of well-belownormal rainfall.
Droughts are usually the result of shifts in global
wind patterns that allow large high-pressure
systems to persist for weeks or months over
continental areas.
Recurring Weather
Floods and Droughts
Heat Waves
– Heat waves, which are extended periods of abovenormal temperatures, can be formed by the same highpressure systems that cause droughts.
– As the air under a large high-pressure system sinks, it
warms by compression and causes above-normal
temperatures.
– The high-pressure system also blocks cooler air
masses from moving into the area, so there is little
relief from the heat.
Recurring Weather
Floods and Droughts
Heat Waves
– If the air is humid, it slows the rate of evaporation,
which diminishes the body’s ability to regulate internal
temperature.
– Because of the danger, the National Weather Service
routinely reports the heat index.
– The heat index assesses the effect of the body’s
increasing difficulty in regulating its internal
temperature as relative humidity rises.
Recurring Weather
Floods and Droughts
Recurring Weather
Cold Waves
• A cold wave is an extended period of belownormal temperatures.
Cold waves are brought on by large, high-pressure
systems of continental polar or
arctic origin.
Winter high-pressure systems are much more
influenced by the jet stream than are summer
systems and therefore rarely linger over one area.
Several polar high-pressure systems can follow the
same path and subject the same areas to bout
after bout of numbing cold.
Recurring Weather
Cold Waves
• The wind-chill factor is measured by the windchill index, which estimates the heat loss from
human skin caused by the combination of cold
air and wind.