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Notes: ch 17, section 2
storm
a violent disturbance in the
atmosphere
involves sudden changes in
air pressure
thunderstorm warm, humid air rises
quickly, cools forming
cumulonimbus clouds
“thunderheads”
strong updrafts and
downdrafts of air
wind shear
when downdrafts of air strike
ground and spread out in
all directions producing
bursts of wind.
lightning
+/- charges build up in
clouds. a sudden spark
makes charges jump between
clouds or between clouds and
the ground.
can heat the air 30 000 oC.
thunder
rapidly heated air expands
suddenly – explosively
tornado
rapidly whirling funnel
shaped cloud which contacts
the ground. ( speeds up to
480 km/hr)
how forms: warm humid air
from Gulf to plains. meets
cold front from Canada.
Cold air moves under warm
air, creates thunderstorm
squall line.
waterspout
a tornado over water (lake,
ocean)
hurricane
Generally form in the area
between 5o to 20o north &
south latitude over warm,
tropical oceans. They are a
tropical storm with wind
greater than 119km/hr.
typically 600km across.
Called typhoons in W Pacific
Ocean, cyclones over Indian
Ocean.
A hurricane begins as a group
of thunderstorms moving
over tropical ocean waters.
Winds traveling in 2 different
directions collide, causing the
storm to rotate over an area
of low pressure. Hurricanes
get their energy from
condensation of water vapor.
Once formed they are fueled
through contact with the
warm ocean water. As the
warm, moist air rises, the
water vapor condenses,
releasing large amounts of
energy. It continues to grow
as long as it is over
its source of warm moisture.
When it moves to cooler
waters, it dies as it has lost its
source of energy.
Damage from hurricanes is
from winds and flooding.
A storm surge is a wall of
water that builds up over the
ocean due to the heavy winds
and low atmospheric
pressure. This wall of water
reaches its greatest height
when it crashes onto shore. It
can be from 1m to 8m high.
This can result in flooding.