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. 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 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.
Tornadoes can appear as a traditional funnel shape,
or in a slender rope-like form. Some have a churning, smoky look to them, and
other contain "multiple vortices", which are small, individual
tornadoes rotating around a common center. Even others may be nearly invisible,
with only swirling dust or debris at ground levels as the only indication of
the tornado's presence.
A funnel cloud is a rotating cone-shaped column of air extending downward from the base of a thunderstorm, but not touching the ground. When it reaches the ground it is called a tornado.
A wall cloud is an abrupt lowering of a rain-free cumulonimbus base into a low-hanging accessory cloud. A wall cloud is usually situated in the southwest portion of the storm. A rotating wall cloud usually develops before tornadoes or funnel clouds.
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.
The geography of the central part of
the United States, known as the Great Plains, is suited to bring all of the
ingredients together to forms tornadoes. More than 500 tornadoes typically
occur in this area every year and is why it is commonly known as "Tornado
Alley". Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota,
Iowa, Missouri, Arkansas and Louisiana all make up Tornado Alley.
Tornado
Safety Tips
BEFORE
A TORNADO:
Have
a disaster plan. Make sure everyone knows where to go in case a tornado
threatens. Make sure you know which county or parish you live in. Prepare a kit
with emergency food for your home. Have enough food and water for at least 3
days.
DURING
A TORNADO:
Go to
a basement. If you do not have a basement, go to an interior room without
windows on the lowest floor such as a bathroom or closet. 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 and lie flat in it. Stay away from
fallen power lines and stay out of damaged areas.
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.
AFTER
A TORNADO:
Stay
indoors until it is safe to come out. Check for injured or trapped people,
without putting yourself in danger. Watch out for downed power lines. Use a
flashlight to inspect your home.
Source: http://www.weatherwizkids.com/weather-tornado.htm
