Although tornadoes occur in many parts of the world, these
destructive forces of nature are found most frequently in the
United States, East of the Rocky Mountains, during the Spring
and Summer months. In an average year, 800 tornadoes are
reported nationwide, resulting in 80 deaths and more than 1,500
injuries. A tornado is defined as a violently rotating column
of air extending from a thunderstorm to the ground. The most violent
tornadoes are capable of tremendous destruction with wind speeds
of 250 mph or more. Damage paths can be in excess of one mile
wide and 50 miles long. Once, a tornado in Broken Bow, Oklahoma,
carried a motel sign 30 miles and dropped it in Arkansas!
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 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 the 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.
Frequency of Tornadoes
Tornadoes can occur at any time of the year.
In the southern states, peak tornado occurrence is in March through
May, while peak months in the northern states are during the summer.
Note, in some states, a secondary tornado maximum occurs in the
fall.
Tornadoes are most likely to occur between 3 P.M. and 9 P.M.,
but have been known to occur at all hours of the day or night.
The average tornado moves from southwest to northeast, but tornadoes
have been known to move in any direction. The average forward
speed is 30 mph but may vary from nearly stationary to 70 mph.
The total number of tornadoes is probably higher than indicated
in the western states. Sparse population reduces the number reported.
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
Tornadoes are some of the most terrifying of weather phenomenon. Winds in an F5 tornado - the highest of five rankings - can reach 300 miles per hour and can lift homes off their foundations and send cars flying through the air. Tornadoes are also deadly, killing an average of 42 people in the U.S. each year. Last year, FEMA responded to 14 tornado-related federal disasters. The tornadoes that struck Georgia in the early morning of February 14, killed more than a dozen people and left whole neighborhoods destroyed. Spring is a traditionally busy tornado time, although tornadoes can occur in virtually any state at any time. What do you need to know about responding to a tornado threat?
The difference between tornado watches and warnings:
What to do if you're at home during a tornado:
What do to if you're outdoors:
What to do if you're in a car:
FEMA is urging people who live in tornado-prone areas to make sure they have a tornado-safe place to go during a tornado. In the absence of a basement, a tornado-safe room build within the house will protect your family during a tornado. Properly built safe rooms can provide protection against winds of 250 miles per hour and against flying objects traveling at 100 miles per hour. The plans for the safe rooms were developed along with the Wind Engineering Research Center of Texas Tech University in Lubbock, Texas.
The seriousness of Tornado Safety cannot be emphasized enough. The above statistics have been paraphrased from FEMA sources as well as other U.S. Government sources. We strongly suggest you click the FEMA link below and read their safety suggestions and view their resources on Safe Room construction and procedures in an emergency.
