Transcript dfafafad - Parrott

For clouds to form, air must be lifted
Convectional
Orographic
Frontal
when an air mass is
forced from a low
elevation to a higher
elevation as it moves
over rising terrain. As
the air mass gains
altitude it quickly
cools down, which
can raise the
humidity to 100% and
create clouds and,
under the right
conditions,
precipitation.
1. Orographic
Lifting
2. Convectional
Lifting
Earth’s surface is
heated by the sun,
which heats the
air mass above it.
The heated air
near Earth’s
surface rises and
cool air sinks.
3. Frontal
Lifting
Warm air mass is
pushed upward by
cold air mass
What is severe weather?
Weather that poses a danger.
The main types of severe weather are:
Thunderstorms
Tornadoes
Hurricanes
What is a thunderstorm?
A storm that produces:
1. Lightning
2. Thunder
3. Heavy Rain and/or flooding
4. Strong winds and possibly hail
They last about 15-60 minutes.
Mr. Fetch’s Earth Science Classroom
How do thunderstorms form?
When warm, moist air is lifted up violently.
The air rises up to form a cumulonimbus cloud.
Mr. Fetch’s Earth Science Classroom
If the winds are
over 58 mph, the
thunderstorm is
said to be a
SEVERE
THUNDERSTORM
.
How does lightning form?
Updrafts and
downdrafts of
wind and rain
cause
different parts
of a cloud to
become
electrically
charged.
- (+) charge at
top of cloud
- (-) charge at
bottom of cloud
How Far Away is Lightning?
•Every second between a lightning flash and thunder means the storm is 1 mile
away.
Speed of Light: 186,000 miles/second or 300,000 km/second
Speed-of-sound: 1100 ft/sec (330 m/sec)
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About 54 people die by lightning strike
each year in US
The odds of being struck in your lifetime
is 1 in 10,000.
Man Struck by Lightning
Lightning can be 5
times hotter than the
surface of the Sun!
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Talking on a corded telephone is the leading cause of
lightning injuries inside the home
Standing under a tall tree is one of the most dangerous
places to take shelter outside
Is Your Car Safe Video?
Lightning Facts
NO SUCH THING AS
HEAT LIGHTNING
= FAR AWAY
THUNDERSTORM
If you hear thunder, then you are
close enough to the storm to get
struck by lightning!
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Thunder
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Caused by the rapid expansion and contraction of the
air surrounding a lightning bolt.
Tornado:
A rotating column of air.
1. Wind shear causes air to rotate.
2. The rotating column of air is lifted by updrafts
3. The column of air touches the ground = tornado
How are tornados classified?
3 out of every 4 tornadoes in the world
happen in the United States
A Tornado can
occur at any time,
but most often
between 3pm and
9pm
A Tornado in Oklahoma
once destroyed a whole
motel. People later found
the motel’s sign in
Arkansas
The United States have an
average of 800 tornadoes
every year
The chances that a tornado is a
F5, the highest classification for
a tornado on the F-scale, is less
than 0.1%
Storm Chasing - your future career?
http://www.youtube.com/watch?v=bhGWWY1nCWw&feature=relmfu
Hurricanes
Pushed by
the easterly
trade winds.
A tropical
area of low
pressure that
forms over
warm water
Slow
moving
storm: Lasts
for days.
Wind
speeds
must be
higher than
74 mph.
Usually given
alphabetical
names for
convenience
http://www.cbsnews.com/htdocs/natural_disasters/hurricanes/fr
amesource_flash.html
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Low Pressure Systems
Associated with hurricanes
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Strong winds and bad weather
Move Counterclockwise
5 Things a Hurricane needs to Form
Progression to a Hurricane
Disturbance
Depression
Tropical
Storm
Hurricane
Saffir-Simpson Scale is used to
measure a hurricane’s intensity
Most dangerous part of hurricanes
Storm Surge – like what happened with
Hurricane Katrina