Transcript Notes - Rudds Classroom

The Atmosphere
B6: Storms
Storms
• Storm – A violent disturbance in the atmosphere as
the result of sudden changes in air pressure and
rapid air movement
– Conditions that bring one kind of storm can often
cause other types of storms in the same area
– Example – conditions that cause thunderstorms
can also cause tornados
Thunderstorms
• Thunderstorm – A storm frequently accompanied
by heavy precipitation, thunder, and lightning
– Formation – Form in cumulonimbus clouds
usually in hot, humid weather
– They also form
when warm air
is forced
upward along
edge of a cold
front
Thunderstorms
– In both cases, warm, humid air rises rapidly
– Inside the thunderheads, drastic changes in air
pressure cause strong updrafts and downdrafts
– The air cools forming dense thunderheads
– Heavy rain falls, sometimes along with hail
– Lightning – A powerful, sudden discharge of
electricity within a thundercloud
– As water droplets move
within the cloud,
collisions occur
knocking electrons free
Lightning
– These collisions create
positively and negatively
charged areas within the cloud
– An electrical field builds between the charged areas
– As the fields gather strength, the air around them
become ionized
– This leads to a sudden, powerful electrical
discharge called lightning
– The discharge can occur within a cloud, between
clouds, or between a cloud and the Earth
Thunder
– Thunder – the sound created
when lightning discharges
– A lightning bolt can heat the
air around it to as much as
30,000o C which is much hotter than the sun
– This rapidly heated air expands suddenly and
explosively
– Thunder is the sound of the explosion
– Since light travels faster than sound, you can see
the lightning before you hear the thunder
Thunderstorms
– Thunderstorm Damage – Can
cause severe damage
– When lightning strikes the ground it can damage
trees and structures in addition to starting fires
– When lightning strikes people or animals it can
cause burns or even death
– Floods – Heavy rains can cause
flooding in low-lying areas
– Floods occur when too much
water pours into a stream or
river, causing it to overflow
its banks.
Floods
– Floods can also occur when it rains in areas
where the ground is already saturated
– The new water cannot soak into the ground
causing it to build up on top
– Areas where the ground has been covered by
buildings, road, and parking lots make this
problem even worse
– Flash Flood – is a
sudden, violent flood
that occurs shortly after
a storm
Tornadoes
• Tornado – Rapidly spinning funnel-shaped cloud
that reaches down from a storm cloud to touch
Earth’s surface
– Formation – Most commonly develop in the same
thick cumulonimbus clouds that produce
thunderstorms
Tornadoes
– Warm, moist air flows in at the bottom of a
cumulonimbus cloud and moves upward
– A low pressure area forms inside the cloud
– The warm air begins to rotate as it meets winds
blowing in different directions at different altitudes
– Forms a spinning funnel inside the cloud with very
strong winds
– If the funnel
touches the
ground, it
becomes a
tornado
Tornadoes
– Tornado Alley – Tornadoes occur more often in the
U.S. than in any other country.
– About 800 tornadoes occur in the U.S. every year,
most of which form in the Great Plains in an area
known as ‘Tornado Alley’
– Tornado Damage – Damage is a result of both strong
winds and flying debris
– The low pressure inside the
tornado sucks dirt and other
objects into it
Tornadoes
– Can pick up large objects like sheds, trailers, cars,
and debris and deposit it miles away
– The damage is unpredictable, destroying 1 house
but leaving a house across the street undamaged
– Scale – Tornadoes are
ranked on the Fujita scale
by the damage they cause
– Scale starts at F0 where
little damage occurs
To an F5 with extreme
damage over a large
area
Hurricanes
• Hurricane – Tropical cyclone that has winds of 70
miles an hour or greater
– A typical hurricane is about 300 miles across
– Formation – Hurricanes begin over warm ocean
water as a low-pressure area or tropical disturbance
– As warm, humid air from the
ocean’s surface rises it forms
clouds
– As more air is drawn into the
system, bands of high wind
and heavy rains form
Hurricanes
– Winds begin to spiral inward towards the area of
lowest pressure at the center
– The lower the air pressure at the center, the faster
the winds
– Winds are strongest in a
narrow band around the
center of the storm in a
ring called the eyewall
– Inside the eyewall, the
‘eye’ of the storm is calm
Hurricanes
– Movement – Hurricanes can last for weeks and
travel over large distances
– Form over the ocean and are pushed along by the
trade winds towards the Caribbean and U.S.
– When it passes over
land, it looses the
warm moist air that
fuels it, and
gradually weakens
Hurricanes
– Damage – Most of the damage is caused by high
winds and severe flooding
– High winds damage trees and buildings creating
debris that becomes flying missiles
– Storm Surge – a dome of water created by a
hurricane that sweeps across coast lines
Predicting Weather
• Predicting Weather – Has often been a tragic failure
for most of history
– In the mid 1800’s the electric telegraph provided
the first real improvement to weather forecasting
– Allowed data to be swiftly
gathered and analyzed by experts
– By the 1930’s the weather bureau
had created a network of weather
observers taking readings
– Used weather balloons – at first
they could only tell wind
direction and velocity
Predicting Weather
– Later, with radios attached, the balloons could
report conditions up to 15 miles high
– In 1950, the first computers were used to simulate
weather patterns
– Slow – It took the computers 24
hours to simulate a 24 hour forecast
– The first dramatic improvement came with
weather satellites in the 1960’s
– For the first time forecasters
could see the interactions of
weather systems worldwide
Predicting Weather
– Today, vast networks of satellites, sea buoys, and
weather balloons gather data all over the world
– More advances computers analyze the data faster
and create more accurate weather models
– However, the
models must still
be interpreted and
the science behind
it is still young
Predicting Weather
– In addition, the models cannot always account for
all the factors that might affect the forecast
– Small variations can result in very different
models using the same data
How many times
have they
predicted a
storm and we all
hoped for a
snow day that
didn’t happen?
In Closing
– Why is it important to understand and be able to
predict weather patterns?