Transcript Severe Weather

Severe Weather
A SCIENTASTIC PRESENTATION
Storm Chaser’s Clip
http://www.discovery.com/tv-shows/storm-chasers/videos/what-is-thedominator.htm
Discussion Question –
Severe Thunderstorms
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Capable of producing:
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heavy downpours and flash flooding
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Strong, gusty straight-line winds
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Large hail
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Frequent lightning
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Tornadoes
For a thunderstorm to be officially classified as severe:
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winds in excess of 93 kilometers (58 miles) per hour
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produce hailstones with diameters larger than 1.0 inch or generate a
tornado.
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about 10 percent (10,000 storms) reach severe status.
Life Cycle of Thunderstorms
Cumulus Stage
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Dominated by rising currents of air (updrafts)
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Formation of a towering cumulonimbus cloud
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Falling precipitation within the cloud causes
drag on the air and initiates a downdraft
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The downdraft is called an entrainment
Life Cycle of Thunderstorms
Mature Stage
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Downdraft leaves the base of the
cloud and this releases the
precipitation
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Gusty winds, lightning, heavy
precipitation, and sometimes hail
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The most active period of a
thunderstorm.
Life Cycle of Thunderstorms
Dissipating
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Dominated by downdrafts
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Without a supply of moisture from updrafts,
the cloud soon evaporates
Squall Lines
A squall line is a line of severe thunderstorms that
can form along and/or ahead of a cold front.
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Contains heavy precipitation, hail,
frequent lightning, strong straight line
winds, and possibly tornadoes and
waterspouts
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Form in unstable atmospheric
environments where low-level air can rise
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Heat is released during condensation
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Causes the rising air becoming lighter
than nearby air at the same height.
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This leads to an increase in the speed of
the rising air (up to 30 mph)
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The gust front
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where these winds meet
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extends from the surface well up into the
storm
Super cells
Super cell is a large rotating thunderstorm with
a mesocyclones
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Can last longer than normal thunderstorms
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Can produce tornadoes and baseball size
hail.
Mesocyclone is a large rotating vortex of air
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Rotate in the same direction as a low air
pressure system
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Formed when wind shear starts a portion of
air in the lower atmosphere spinning in a
tube
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In the tube the air is rotating around a
vertical axis.
Super Cells
Components of a Supercell
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The overshooting top is a dome
shaped formation on the top of a
supercell
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The anvil is the overshooting portion
at the top of the supercell (cold,
dry)
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The precipitation free base is a
portion of the supercell without
precipitation
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The wall cloud is the portion of the
super cell between the precipitation
free base and precipitating areas
Lab – Make Your Own Cloud
http://www.kidspot.com.au/kids-activities-and-games/scienceexperiments+10/how-to-make-a-cloud-in-a-jar+12511.htm
Tornados
Tornadoes are large clouds mostly
characterized by extremely high winds
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Usually found in the most intense super
cells and are caused by winds
traveling in different directions
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Look like large funnels touching down
from the main cloud
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A funnel cloud may or may not occur
with a tornado
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Damage caused by a tornado can be
related to the high
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Hazards include downed power lines,
broken gas lines and pumps, and fires
Formation of Tornados
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Formation
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The rotation of winds within a meso cyclone
allows a vortex to form
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A funnel cloud usually forms
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Gains energy as it descends
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Becomes a tornado once it touches down
Maturity
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When it becomes a tornado
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Where all the destruction comes in.
Dissapation
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Meso cyclone loses its rotation
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Begins to dissipate
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Shape of the tornado can be altered
Water Sprouts
Waterspouts are similar
vortexes that occur over
water. They are usually
less violent than regular
tornadoes, although
they can be rather
powerful given a strong
storm
Fujita Scale
An F6 category was also thought of, but it is
purely hypothetical and no F6 tornado has
actually existed. The Enhanced Fujita Scale
was intended to improve the Fujita scale. Both
scales measure the severity of tornados.
Lab – Make Your Own Tornado
http://www.kidspot.com.au/kids-activities-and-games/scienceexperiments+10/tornado-in-a-jar-experiment+12759.htm