Download disasterbraden copy - Bailey Station Elementary

Braden
Robbins
Tornadoes are an atmospheric event. A
tornado is a rapidly rotating column of
air, known as a vortex, that has
reached the ground. It is often
associated with a funnel cloud, a
funnel-shaped cloud that may appear
near the ground in a thunderstorm.
Tornado winds swirl at speeds that may
exceed 300 miles (480 kilometers) per
hour on rare occasions. Tornadoes are
also sometimes called twisters.
Tornadoes can happen at any time of the year and at any time
of the day. In the southern states, peak tornado season is
from March through May. Peak times for tornadoes in the
northern states are during the summer. A few southern
states have a second peak time for tornado outbreaks in the
fall. Tornadoes are most likely to occur between 3 p.m. and 9
p.m.
During a tornado go to a basement. If you do not have a
basement, go to an interior room without windows, such
as a bathroom or closet, on the lowest floor. If you can,
get under a sturdy piece of furniture, like a table. If you
live in a mobile home, get out. They offer little protection
against tornadoes. Get out of automobiles. Do not try to
outrun a tornado in your car; leave it immediately. If
you’re outside, go to a ditch or low lying area. If you’re
at school during a tornado, every school should have a
disaster plan and have frequent drills. Basements
offer the best protection. Schools without basements
should use interior rooms and hallways on the lowest
floor away from windows. Crouch down on your knees
and protect your head with your arms.
The most damaging tornadoes form in storms called supercells. A supercell is a large,
powerful thunderstorm. It contains a rapidly rotating air mass called a mesocyclone. For
a supercell to form, and perhaps spawn a tornado,
several basic conditions must exist.
1
There must be an adequate supply of moisture to feed the storm. There must be a layer
of warm, moist air near the ground and a layer of cool air above. Finally, the winds at
higher elevations must differ from those at lower levels in speed, direction, or both.
The "Tri-State Tornado" traveling more than 300 miles through Missouri, Illinois and Indiana on
January
2015old
Volume
VII
March 18, 1925 killed 695 people and injured 2027. It was rated an F5 at the
top 20,
of the
Fujita
scale (with winds of 260-plus mph).
The "Natchez Tornado" occurred on May 6, 1840, along the Mississippi River in Louisiana and
Mississippi. It killed 317 people and injured 109. The official death toll may not have included slaves,
according to the Federal Emergency Management Agency.I
!
!
The "St. Louis Tornado" occurred on May 27, 1896 in Missouri and Illinois. It killed 255 people
and injured 1,000. It had winds of between 207 mph and 260 mph.
The "Gainesville Tornado" was a pair of storms that converged April 6, 1936, in Gainesville,
Georgia, killing 203 people and injuring 1,600. The tornado destroyed four blocks and 750 houses in
the northern Georgia town. The "Woodward Tornado" wreaked havoc across parts of Texas, Oklahoma
and Kansas on April 9, 1947. The storm, which killed 181 people and injured 970, reportedly was more
than a mile wide in places.
If there is warm, moist air at a lower altitude and cold, dry air at a higher altitude, the warmer air may
become buoyant and rise rapidly. The air cools as it rises. The faster the warm air rises, the larger and
more violent the storm and the more likely it will spawn a tornado. Storms may develop when warm air
rides up over a shallow layer of cooler air. Storms may also form when moist air lifts over mountains,
hills, or other high spots.
Often, a front powers an updraft of warm, moist air. A front is the boundary between two air masses of
different densities resulting from a difference in temperature, humidity, or both. As the warm, less dense
air rises, it begins to cool. The moisture it holds condenses into water droplets, forming a cloud. When the
air rises high enough and becomes cold enough, its moisture turns into ice crystals. High in the
atmosphere, often far above 35,000 feet (10,700 meters), the cloud stops rising. Upon reaching its
maximum height, its top spreads out in the shape of an anvil. Anvil-shaped storm clouds often produce
thunder, heavy rain, lightning, and hail. In the right conditions, a deadly tornado may form under the base
of the cloud.
Another requirement for a supercell is that winds at higher elevations greatly differ from those at lower
levels in speed, direction, or both. A difference in wind speed or direction is called wind shear. Wind shear
makes the column of rising air begin to rotate. At first, the swirling air forms a broad, horizontal tube. As
the storm develops, the tube tilts upright. It becomes the rotating column of air called a mesocyclone.
2