Download Tornadoes

11/16/15
• Winds can exceed 300 mph!!!
• Around 1,000 occur on average each year in the U.S.
• Kill 80, injure 1,500 people each year on average
• Can have a path up to a mile wide!!!
• Can occur any time of the year, but peak during the
spring (March-June)
• Occur most frequently in the central U.S. in a region
nicknamed “Tornado Alley”
• A tornado is a violently rotating
column of air extending from a
thunderstorm to the ground.
Change in wind direction
Increase in wind speed
Increasing height
Rising air within a thunderstorm
How do they form?
We have a pretty good idea…
How do they form?
• Most tornadoes form from
thunderstorms.
• You need warm, moist air
from the Gulf of Mexico and
cool, dry air from Canada.
• When these two air masses
meet, they create instability
in the atmosphere.
Step 1
• Before a t-storm, a change in
wind direction and an increase
in speed forms an invisible,
horizontal spinning effect in
the lower atmosphere (at the
base of the storm)
Step 2
• Rising air within the t-storm
(updrafts) tilts the rotating air
from horizontal to vertical
Step 3
• Vertical rotation now extends
2-6 miles up into the t-storm.
• Now a tornado may form and
extend from this area of
rotation to the ground.
A Tornado Develops
Tornado damage is measured by the Fujita
scale
Dr. T. Theodore Fujita came up
with a scale which measures the
strength of tornadoes
Not Fajita!
The Damage done is connected to the
strength/wind speed of the tornado
• SCALE WIND SPEED
POSSIBLE DAMAGE
• F0
40-72 mph
Light damage: Branches broken off trees; minor roof damage
• F1
•
73-112 mph
Moderate damage: Trees snapped; mobile home pushed off
foundations; roofs damaged
• F2
•
113-157 mph
Considerable damage: Mobile homes demolished; trees
uprooted; strong built homes unroofed
• F3
•
158-206 mph
Severe damage: Trains overturned; cars lifted off the
ground; strong built homes have outside walls blown away
• F4
•
207-260 mph
Devastating damage: Houses leveled leaving piles of
debris; cars thrown 300 yards or more in the air
• F5
•
261-318 mph
Incredible damage: Strongly built homes completely
blown away; automobile-sized missiles generated
F0: Gale tornado (40-72 mph); light
damage. Some damage to chimneys;
break branches off trees; push over
shallow-rooted trees; damage to sign
boards.
F1: Moderate tornado (73-112 mph); moderate
damage. The lower limit is the beginning of
hurricane wind speed; peel surface off roofs;
mobile homes pushed off foundations or
overturned; moving autos pushed off the roads.
F2: Significant tornado (113-157 mph);
considerable damage. roofs torn off frame houses;
mobile homes demolished; boxcars pushed over;
large trees snapped or uprooted; light-object
missiles generated.
• F3: Severe tornado (158-206 mph); Severe damage.
Roofs and some walls torn off well-constructed houses;
trains overturned; most trees in forest uprooted; heavy
cars lifted off ground and thrown.
• F4: Devastating tornado (207-260 mph); Devastating
damage. Well- constructed houses leveled; structure
with weak foundation blown off some distance; cars
thrown and large missiles generated.
• F5: Incredible tornado (261-318 mph); Incredible
damage. Strong frame houses lifted off foundations
and carried considerable distance to disintegrate;
automobile sized missiles fly through the air in excess
of 100 yards; trees debarked; incredible phenomena
will occur.
Tornadoes are found most frequently in the
U.S.
• In the United States, the area where
the tornadoes hit the most is called
Tornado Alley. The states which are
in the tornado alley are:
• Arkansas, Iowa, Kansas,
Louisiana, Minnesota,
Nebraska, North Dakota, Ohio,
Oklahoma, South Dakota, and
Texas.
Number of Tornadoes in
Specific Years
180
160
140
120
100
Tornadoes
80
60
40
20
0
1979
1985
1992
2004
Biggest, Costliest Outbreaks
• The April 3-4, 1974 Super Outbreak was the
largest known outbreak, with 148 tornadoes in 11
states, killing 315 people, injuring more than 5,300
and causing $600 million in damages.
• Alabama, Kentucky and Ohio were the states
hardest hit.
• Perhaps the most notable tornado of the outbreak
was one which touched down southwest of Xenia,
Ohio. The violent tornado destroyed half the town,
killing 34 and causing property damages of more
than $100 million.
Types of Tornadoes
What is a waterspout?
• A waterspout is just a
weak tornado that
forms over water.
• They are most common
along the Gulf Coast.
• Waterspouts can
sometimes move
inland, becoming
tornadoes causing
damage and injuries.
What is a gustnado?
A gustnado is a short-lived,
relatively weak whirlwind that
forms along a gust front. A gust
front is the surge of very gusty
winds at the leading edge of a
thunderstorm's outflow of air.
Gustnadoes are not tornadoes.
They do not connect with any
cloud-base rotation. But because
gustnadoes often have a spinning
dust cloud at ground level, they
are sometimes wrongly reported
as tornadoes.
Gustnadoes can do minor
damage.
A gustnado in southeastern Wisconsin on 4
October 2002.
Tornado watch and warning
TORNADO WATCH Tornadoes are possible
in your area. Stay tuned
to the radio or television
news.
TORNADO WARNING A tornado is either on the
ground or has been
detected by Doppler
radar. Seek shelter
immediately!
Red: Tornado Warning
Purple: Flash Flood Warning
Where is the safest place to go
during a tornado?
Safest Places
DuringaTornado
Basement
Ditch
Shower
Inner Hallway
Center of Room
THE END