Transcript Tornados

Tornados
R.T. Schindler
Spring storm and tornadoes in Kansas
Additional Lectures by world experts
"Tornadoes" lecture by Lillibridge, Scott R
"A Historical Look at Tornadoes: Damage and Death”
by Harold Brooks
which have also three more links to online lectures:
1.Development of synthetic severe thunderstorm
climatologies
2.Tornado deaths in the US and mobile homes
3.The distribution of tornadoes by F-scale in time
and spaceHarold Brooks
“Tornado-Related deaths and injuries due to
the May 3, 1999 by Sheryll Brown, Pam Archer,
Elizabeth Kruger and corresponding author
Sue Mallonee from Injury Prevention Service,
Oklahoma State Department of Health
Tornado History
First Tornado Forecast
Tornado
A violently rotating column
of air (vortex), hanging from
a cumulonimbus cloud, with
circulation that touches the
surface of the earth
Tornado Formation
Supercell Storm
• Severe weather occurs as strong
downbursts…large hail…occasional flash
floods and weak to violent tornadoes
• Severe event almost always occur near the
updraft interface typically in the rear
(southwest) storm flank. Some of the
supercells have the interface on the front of
the southeast flank
• High predictability of occurrence of severe
events once a storm is identified as a
supercell
• Extremely dangerous to public
• Extremely dangerous to aviation
The Supercell
Tornado forms here
Tornado Facts
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Tornados can occur almost anywhere in the world
Duration: a few minutes
Diameter (Avg.): 0.4 km
Length of path (Avg.): 6 km
Funnel can travel from 0 mph up to ~70 mph,
usually travels at 30 mph
99% of all tornados in Northern Hemisphere rotate
counterclockwise
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
Texas cost per person per year for tornados: $3.94
Tornado Myths
• A highway overpass is a safe place
to take shelter under during a
tornado
• Opening windows during a tornado
will help balance the pressure
between the inside and outside of the
house and may prevent destruction
of the structure
• One should seek shelter in the
southwest corner of a house or
basement
Tornado Oddities
• Tornados are reported to routinely carry
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objects many miles and have:
sucked the frogs out of a pond and
dropped them on a town
carried a necktie rack with 10 ties attached
40 miles
carried a flour sack 110 miles from a mill
Tornados also drive objects into other
objects and have:
Driven splinters into an iron fire hydrant
Driven straw and grass into telephone poles
When Tornados Occur
A typical late afternoon tornado
Where Tornados Occur
Tornado Alley covers the Great Plains states
Tornado Wind Speed
In 1971, Dr. Fujita
developed a way of
measuring the winds of
a tornado. He reasoned
that there was a link
between wind speed
and the damage caused
by a tornado. There are
6 categories of tornados
(F0 – F5)
F0 Category
F3 Category
• (Strong) winds: (158-206) mph, severe damage
• Damage: most trees uprooted, trains
overturned, roofs torn off, walls demolished
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
Tornado Forecasting
Meteorologists who predict
tornado development
analyze the current
atmospheric conditions such
as: air temp., barometric
pressure, the locations of
fronts, wind velocities,
convection, etc. Probably
the most useful tool a
meteorologist can use to
identify tornados is radar,
specifically Doppler radar
(WSR-88D)
Tornados on Radar
Doppler image of a rain-wrapped tornado
The Life cycle of a Tornado
• The “Life Cycle” of a tornado consists of four
distinct stages.
• These stages were first determined during the
Union City, OK tornado of 1973
• Most tornadic events are difficult to classify
and may not exhibit stages that are obvious to
the observer
• Sometimes events become unclear: one
tornado weakens another appears, or single
event?
• Tornados do not “skip” – gaps in damage path
may indicate a temporary weakening in
intensity
Beginning Stage:
Tornado begins as
a rotating wall
cloud which
quickly evolves
into a funnel
Early Stage:
Tornado funnel develops (may be
transparent) and extends down from the
cloud to the ground
Mature Stage: Tornado funnel reaches
maximum width as well as maximum
intensity then begins to shrink
Decay Stage:
tornado may
remain
stationary
and take on a
ropelike
appearance
before
dissipating
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
Satellite image taken May 3, 1999 @ 645 CDT
View from the air of a
tornado path in Central OK
Tornado near Amber, OK at 6:30 CDT
Microburst
Microbursts are
downdrafts from
thunderstorms
consisting of a
narrow column of
cool air traveling at
high speeds which
can cause damage
similar to a weak
tornado over a
small area
Waterspouts
A waterspout is a tornado that forms over a
body of water, or a tornado that moves
from land onto water
Storm Chasers
Storm chasers are a group made up of
meteorologists and scientists, as well as amateur
observers who voluntarily put themselves in the
path of a severe thunderstorm in order to hopefully
observe a tornado and obtain photographs and
scientific data.
Tornado Indicators
• A greenish colored sky associated with
the thunderstorm (caused possibly by the
scattering of light by particles in the sky)
• Mammatus clouds
• A sudden drop in barometric pressure
• Large hail of at least .75 in. diameter
• Strong winds > 60 mph
• Frequent and intense lightning
• A rotating wall cloud or a cloud that
appears to hang from the sky
• A loud rumbling noise- seek shelter!
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
Early Warning Systems
The National Storm Prediction Center constantly
monitors the weather and radars across the U.S.
They are responsible for issuing tornado watches
and warnings.
• Tornado Watch: a parallelogram is drawn around
a 10,000 mi.^2 s area where the atmosphere
seems to possess the conditions necessary for
tornado development (severe thunderstorm)
• Tornado warning: a county has a thunderstorm
which appears to have produced a tornado or
someone has physically spotted a tornado,
apparent funnel, or observed damage from what
could be a tornado! SEEK SHELTER
IMMEDIATELY!!
Early Warning Systems
Bibliography
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http//www.photolib.noaa.gov/
http://www.nsl.noaa.gov/GoldenAnniversary
http://www.srh.noaa.gov/oun/
http://www.usatoday.com/weather
www.nsl.noaa.gov/~doswell?a_tornado/atornado.html
http://www.disastercenter.com/
http://www.tornadoproject.com/
Church C., Burgess D., Doswell C., Davies-Jones,R.,
ed. The Tornado: Its Structure, Dynamics, Prediction,
and Hazards.
• American Geophysical Union Press: 2000
• Liu, Henry. Calculation Of Wind Speeds Required to
Damage or Destroy Buildings. Publication within
The Tornado