• A violently rotating column of air
extending from a thunderstorm to
the ground.
• Wall cloud
• Funnel cloud
• Suction Vortices (Vortex)
• Conditions that must be present for Tornado
formation:
-Cool, dry air colliding with warm, moist air.
• Conditions that signal a Tornado are:
- Greenish clouds
- Hail
- Rotation
- Funnel clouds
- Sounds like a freight train
Where are they found
• Tornadoes result from the interaction of
contrasting air masses, mainly found in midlatitude regions where tropical and polar air
meet as part of the global atmospheric
circulation.
• Tornadoes are the most violent atmospheric
storms, although the damage is high, the area
affected is much smaller.
Where are tornadoes
most likely to happen?
• Tornado Alley
• Tornado Alley is an area in the great plain
states that runs from Texas to Nebraska+.
Between the Rocky mountains and the
Appalachian mountains. On both sides of
the Mississippi river.
• -As well as some of the southern states,
and many parts of the world.
• -They occur mostly in the afternoon and in
the early evening.
• Tornadoes can actually occur at any
time of the year, but peak tornado
season is March thru May for the
Southern states and in the northern
states it is during the summer
formation
• Supercell formation
• Non-supercell formation
• Dry line formation
Consist of 5 stages
• Stage One: The dust, whirlwind stage
• Stage Two: Organizing Stage.
• Stage Three: Mature Stage.
• Stage Four: Shrinking Stage.
• Stage Five: Decaying Stage.
Where does the energy
come from
Latent heat
• Latent Heat of Condensation is the main energy
source for the Thunderstorm and Tornado.
• When the water vapor inside the storm condenses
it releases the heat it used when it evaporated.
• When this latent heat warms the rising air parcel,
it can create such high velocities that a Tornado
is formed.
How are tornadoes
categorized
• In 1971, Dr. T. Theodore Fujita devised a
six category scale to classify Tornadoes,
known as the Fujita Tornado Scale.
• How the scale works is, it is based upon
the maximum wind speeds inside the funnel.
They can tell the wind speeds by
investigating each Tornado to measure the
damage and match it to what the scale
says.
• F0 -F1 Weak Tornado
• F2 -F3 Strong Tornado
• F4 -F5 Violent Tornado
Case study: the Oklahoma
tornadoes, May 1999
• In May 1999 a swarm of 65 tornadoes occurred
along a 150-mile belt running from the south-west of
Oklahoma State towards Kansas.
• 45 people dead
• 8000 buildings ruined or damaged
• A large 1-2km wide tornado touched down for a track
over 61km long including parts of Oklahoma city was
the first tornado cause one billion dollars worth of
damage.
Ideal conditions in the Great
Plains for tornado
information
• Warming moist air from Gulf of Mexico
• Cool drier air on top of the warm air,
leading to instability
• Separation layer of warm dry air so that
the two main layers do not mix
• Wind shear at upper levels
• A clear frontal boundary between two
contrasting air masses
• Rotation in the jet stream
• The tornadoes were huge, visible and
audible
• Local radio and television gave huge
coverage
• Warning from the National Weather Service
(NWS) gave an average lead time of
Oklahoma City of 32 minutes. This is twice
the normal time.
• Warning have improved with the use of
Doppler radar which can detect wind
changes.
• The SPC gave early alerts
• The Tri-State tornado of March 18th, 1925 was
the deadliest tornado killing 689 people in
Missouri, Illinois, and Indiana.
• The Tri-State tornado outbreak was quite deadly,
but the costliest, biggest and most prolific
outbreak was the April 3rd & 4th outbreak of 1974.
•
This system spawned 148 tornados in a 16 hour
period in 11 states. 30 of these tornados caused
at least F4 damage and at one time 5 large
tornados were on the ground.
• It killed 315 people and injured more than
6140. It also caused 600 million dollars in
damage.
• The hardest hit states were Alabama,
Kentucky and Ohio.
• The most notable one was the tornado
that hit Xenia, Ohio. It destroyed half the
town, caused 100 million dollars in damage
and killed 34 people.
• The lifting force can cause train
carriages being moved hundreds of
meters.
• Tornado passes over a building the
outside pressure is up to 200mb lower
than that inside, explosion effect on
the building.
• Damage from high wind speeds
• People and animals can be appear to be burnt due to the
rapid dehydration resulting from the pressure fall.
• The resultant flying objects and debris
• -The damage path of a Tornado can be anywhere
from a single
• spot to 160+ km.
• -They are capable of:
• •Toppling buildings
• •lifting mobile homes and cars
• •hurling:
-people
-animals
-trees
-debris
• for hundreds of yards.
The destructive effects of tornadoes due to
• the high wind speeds
• the lifting force of the funnel wall
• The abrupt change in atmospheric pressure.
On average 800 Tornadoes occur every year.
• 80 deaths
• 1500 injuries
Of all Tornadoes:
• 69% weak
• 29% strong
• 2% violent
Tornadoes can be on the ground for an instant to
several hours, but the average time is 5 minutes.
• -Average width of a tornado can
range from 10 meters to 1.6km+.
Typically they are 50meters wide.
• -Tornadoes can move at about 16-96+
mph, but the average is 16-32 mph.
• -Average Tornado moves from
southwest to northwest.
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Hazard-resistant design
Requiring solid construction of buildings
Using basements as part of the structure
Modify people’s vulnerability
Prediction (using radar and satellite technology)
Warning
Community preparedness
Share the loss
Prediction and
forecasting
• The first Tornado forecast found in 1948, by using Surface
and Upper air data along with similarities of the Tornado
that struck a few days before they were able to correctly
predict the occurrence of a Tornado.
• Today we use observations, numerical forecast models,
Doppler Radar, weather balloons and Satellites to predict
our weather. The biggest method being Doppler Radar,
which uses the shifting of wavelengths of the waves
emitted to determine the movement of clouds and all
particles inside.
• Victoria Bishop, Hazard and
Responses Second Edition 2001
• http://orca.rsmas.miami.edu
• http://weather.about.com