What causes tornadoes?
Thunderstorms develop in warm, moist
air in advance of eastward-moving cold fronts. These thunderstorms often
produce large hail, strong
winds, and tornadoes. Tornadoes
in the winter and early spring are often associated with strong, frontal
systems that form in the Central States
and move east. Occasionally, large
outbreaks of tornadoes occur with this type of weather pattern. Several
states may be affected by numerous
severe thunderstorms and tornadoes.
During the spring in the Central
Plains, thunderstorms frequently develop along a "dryline," which separates
very warm, moist air to the east
from hot, dry air to the west.
Tornado-producing thunderstorms may form as the dryline moves east during
the afternoon hours.
Along the front range of the Rocky
Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms
frequently form as air
near the ground flows "upslope"
toward higher terrain. If other favorable conditions exist, these thunderstorms
can produce tornadoes.
Tornadoes occasionally accompany
tropical storms and hurricanes that move over land. Tornadoes are most
common to the right and ahead of
the path of the storm center as
it comes onshore.
Tornado Variations
Some tornadoes
may form during the early stages of rapidly developing thunderstorms. This
type of tornado is most common along the
front
range of the Rocky Mountains, the Plains, and the Western States.
Tornadoes
may appear nearly transparent until dust and debris are picked up.
Occasionally,
two or more tornadoes may occur at the same time.
Waterspout
Waterspouts
are weak tornadoes that form over warm water.
Waterspouts
are most common along the Gulf Coast and southeastern states. In the western
United States, they occur with cold late fall
or late
winter storms, during a time when you least expect tornado development.
Waterspouts
occasionally move inland becoming tornadoes causing damage and injuries.
How Do Tornadoes Form?
Before thunderstorms develop, a
change in wind direction and an increase in wind speed with increasing
height creates an invisible, horizontal
spinning effect in the lower atmosphere.
Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.
An area of rotation, 2-6 miles wide,
now extends through much of the storm. Most strong and violent tornadoes
form within this area of strong
rotation.
A lower cloud base in the center
of the photograph identifies an area of rotation known as a rotating wall
cloud. This area is often nearly
rain-free. Note rain in the background.
Moments later a strong tornado develops
in this area. Softball-size hail and damaging "straight-line" winds also
occurred with this storm.
Tornadoes Take Many
Shapes and Sizes
Weak Tornadoes
69% of
all tornadoes
Less than
5% of tornado deaths
Lifetime
1-10+ minutes
Winds
less than 110 mph
Strong Tornadoes
29% of
all tornadoes
Nearly
30% of all tornado deaths
May last
20 minutes or longer
Winds
110-205 mph
Violent Tornadoes
Only 2%
of all tornadoes
70% of
all tornado deaths
Lifetime
can exceed 1 hour
Winds
greater than 205 mph
Tornado Myths:
MYTH: Areas near rivers, lakes,
and mountains are safe from tornadoes.
FACT: No place is safe from tornadoes.
In the late 1980's, a tornado swept through Yellowstone National Park leaving
a path of destruction up
and down a 10,000 ft. mountain.
MYTH: The low pressure with a tornado
causes buildings to "explode" as the tornado passes overhead.
FACT: Violent winds and debris
slamming into buildings cause most structural damage.
MYTH:Windows should be opened before
a tornado approaches to equalize pressure and minimize damage.
FACT: Opening windows allows damaging
winds to enter the structure. Leave the windows alone; instead, immediately
go to a safe place.
Tornadoes Occur Anywhere
Carolinas Outbreak:
March 28,
1984, afternoon-evening
22 tornadoes
57 deaths
1,248
injuries
damage
$200 million
37% of
fatalities in mobile homes
Pennsylvania-Ohio Outbreak:
May 31,
1985, late afternoon-evening
41 tornadoes,
including 27 in PA and OH
75 deaths
in U.S.
1,025
injuries
damage
$450 million
Plains Outbreak:
April 26-27,
1991, afternoon of 26th through early morning 27th
54 tornadoes
21 deaths
308 injuries
damage
$277+ million
15 deaths
in/near mobile homes, 2 deaths in vehicles
Weather Radar Watches the Sky
Meteorologists rely on weather radar
to provide information on developing storms. The National Weather Service
is strategically locating
Doppler radars across the country
which can detect air movement toward or away from the radar. Early detection
of increasing rotation aloft
within a thunderstorm can allow
life-saving warnings to be issued before the tornado forms.
pictures from tornadoproject.com
information from www.nws.noaa.gov/om/tornado.htm
answers scroll down
1. what is the life line of a tornado?
a.1hour b.10minutes c.5minutes
or d. b and c.
2. what is the average death by
tornadoes of humans every year.
a.100 b200 c 300
3. true or fale only 2percent of
all tornadoes are violen?
4.true or false tornadoes stick
to only one shape.
5.true or false tornadoes aren't
devastating.
6. true or false tornadoes myths.
answers
1. D. b and c average lifeline 1to10minutes
2.a.100 hundred people dye every
year thats and average
3. True only 2 percent of
storms and tornadoes are violent.
4. False Tornadoes come in many
different shapes.
5.false
6. false
