Transcript Tornadoes

Thunderstorms
Thunder N Lightning or Lightning N
Thunder
Tornadoes
2/3/11
► Aim:
What are tornados?
► Do Now:
Based upon the diagram on the board:
What type of front is at location L?
B. What type of front is at location M?
C. Name the possible air masses at P, V, & G.
A.
Which air is more dense, air associated with
cold or a warm front? This air has a high
or low pressure?
► Motivation: Learning of storms that have
affect the U.S.
What is a Tornado?
► Definition:
► Violent
windstorms that take the form of a
rotating funnel of air that extends
downward from a cumulonimbus cloud.
What is a Tornado
► They
are local storms of short duration
usually a few minutes
► Tornadoes have a small diameter usually
less than a mile
► Winds can exceed 300mph
► Tornado
Where and how do they form?
► They
generally form in the vicinity of intense cold
fronts and squall lines (moving lines of
thunderstorms).
► Central US, called Tornado Alley, 700-800 a year.
► In the spring cP air from the north is still very cold
and dry, and mT air from the south is warm,
humid and unstable. When these two air-masses
meet, tornadoes are spawn.
Hail Storm
September 16, 2010
Winds Up to 70mph
Songer http://www.pitt.edu/~super1/lecture/lec0761/005.htm
Tornado Formation
Where Tornados Occur
Tornado Alley covers the Great Plains states
Tornado Facts
► Duration:
a few minutes
► Diameter (Avg.): 0.4 km
► Length of path (Avg.): 6 km
► Funnel can travel from 1 mph up to 70 mph,
usually travels at 30 mph
► Texas is #1 for frequency of tornados per
year
► Between 1950 and 1995 Texas had 5,722
recorded tornados
► Risk of death in a tornado in Texas: 1 in
1,054,267
Tornado Myths
A highway overpass is a safe place to take
shelter under during a tornado
► Overpass
►
Dust Devil/ Water Sprout
Fujita Scale
Fugita Scale
F0 Category
► (Weak)
winds (40-72) mph , little damage
► Damage: tree branches snapped, chimneys
toppled, signs torn down
F3 Category
► (Strong)
winds: (158-206) mph, severe damage
► Damage: most trees uprooted, trains
overturned, roofs torn off, walls demolished
Tornado Path
width and length of the tornado path
F5 Oklahoma 1999
F5 Category
(Violent) winds: (261- 319) mph, incredible damage;
rare
Damage: bark peeled off trees, houses lifted off
foundations, vehicles travel greater than 100 m through
the air
►
Tornado Occurrence by
Category
Tornado Deaths by Category
The Tornado Outbreak of May 3,
1999
► Severe
thunderstorms move into Ok,
TX, Ks and spawn estimated 70
tornados, most occurred in Oklahoma
► In Oklahoma 40 people killed, 675
injured
► Damage: $1.2 billion
► Largest tornado outbreak in Oklahoma
history
► 1,780 homes completely destroyed
► 6,550 homes damaged
Waterspouts
A waterspout is a tornado that forms over a body of
water, or a tornado that moves from land onto water
Tornado Hazards
► Violent
Winds
► Flying Debris, cause for most deaths and
injuries
► Tornadoes have driven a piece of straw
through a wooden plank, uproot trees, pick
up cars, buses, and trains
Mammatus clouds
Green sky
Tornado Damage
A 20-ton trailer blown off
U.S. 30; it bounced 5 times
A pick-up truck caught in the
path of a tornado
Tornados mainly cause damage by
picking up something and throwing it
through the air or hurling objects
against something
Tornado Safety
► In
Homes or Buildings- go to basement, or
interior room such as bathroom, closet, etc.
► In Cars or Mobile Homes- abandon them
Immediately.
► If in an open field- lie flat in the nearest
ditch or depression and use hands to cover
head.
Tornado History
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The “Tri-State Tornado” is
the most violent tornado on
record
On March 18, 1925, the
tornado formed in Missouri
and traveled 219 miles
across Illinois into Indiana
The funnel was up to .75
miles across and traveled as
fast as 73 mph.
It killed approximately 635
people