Download Taking Severe Weather Seriously

Taking Severe Weather Seriously
Kathy Johnston, Science Teacher
North Middle School
Lenoir City, TN
Dangerous weather develops in an instant and may occur at any location on Earth.
Severe weather conditions can range from high winds to hurricanes, from heavy rain to
floods, or from snowfall to blizzards. By discussing the various types of severe weather,
we better prepare ourselves in the event of a weather disaster.
Thunderstorms
Thunderstorms, tornadoes and lightning
are the most violent types of severe
weather. A thunderstorm is formed when
moist air rises and cools to its dew point.
The cooling, moist air condenses forming
clouds. The colder, heavier air begins to
sink forming downdrafts with the resulting
precipitation.
Thunderstorms are classified into four
types – single cell, multicell, squall line,
and super cell. Single cell storms are rare
since even the weakest of storms usually
occur as multicell updraft events. Some
single cell thunderstorms are called "air mass" storms. These storms usually last only
20 to 30 minutes and generally do not generate severe weather. However, one must
remember that any thunderstorm is capable of producing a tornado. Most
thunderstorms are multicell storms lasting several hours. Storms of this type are
capable of producing large hail, damaging winds, flash floods, and isolated tornadoes.
When thunderstorms form in a line, they are called squall lines. These storms usually
generate damaging winds and dangerously large hail. Tornadoes may be present with
squall line storms; however, they are usually weak and short-lived. Most wind damage
from squall line storms is caused by extremely strong downbursts. The rarest and most
dangerous type of thunderstorm is the supercell. Fortunately, they are the easiest to
forecast and track by radar. The deep rotating updraft can be identified on Doppler
radar as an intense orange or red.
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Lightning
Lightning is the most frequent and most dangerous type of weather phenomena.
Although it affects the entire United States, the states that have the most injuries and
deaths are Florida, Michigan, Pennsylvania, North Carolina, New York, Ohio, Texas,
Tennessee, Georgia and Colorado. The almost continual occurrence of lightning strikes
is amazing. There are approximately 100 lightning strikes per second on the Earth. That
is 8 million, 6 hundred and 40 thousand times per day! In the United States alone, the
damage from lightning can be over four million dollars per year.
What is lightning? Essentially it is a
form of electrical discharge that
results from the buildup and release
of electrical energy between
positively and negatively charged
portions of a cloud. It can strike
inside a cloud from several sections
of the cloud, from cloud to cloud or
from cloud to ground. One flash of
lightning has enough power inside
to run a 100-watt light bulb for over
three months. The air surrounding
the lightning strike is hotter than the
surface of the Sun! Thunder occurs
inside the cloud at the same
moment as the lightning strike, but
because light travels almost a
million times faster than sound, we
see the lightning before we hear the
thunder. Although it travels slowly, the sound of thunder can be heard up to twelve miles
from the actual thunderstorm. Also lightning can strike as much as 12 miles ahead of a
storm.
People are encouraged to follow precautions when lightning is spotted. If caught in the
open, a person should crouch down into a ball-like position with the feet on the ground.
Lying down is not an effective method of avoiding a lightning strike.
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The lower part of a thundercloud is usually negatively charged. The upward area is
usually positively charged. Lightning from the negatively charged area of the cloud
generally carries a negative charge to Earth and is called a negative flash. A
discharge from a positively-charged area to Earth produces a positive flash. - (NOAA)
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Tornadoes
The tornado is nature’s most violent storm. It may contain
wind speeds of two hundred and fifty miles an hour or more
and can last from one minute to an hour. The fear of
tornadoes can keep children awake at night and make
anyone tremble with fear. Tornadoes are indeed fearsome
and deserve every ounce of concern if the possibility of their
formation is indicated.
Through scientific research and weather data analysis, the
warning systems for severe weather have improved
tremendously in the past two decades. Doppler radar
images give us minute by minute tracking of serious
weather happenings. Lightning detection systems inform us
of the potential for deadly strikes. Computerized models
enable meteorologists to track weather systems and alert
areas of possible thunderstorms up to a week in advance.
These systems are in place for our information and safety.
They are easily available through various media. It is up to
us to take severe weather seriously.
Tornadoes will be the
topic of next month’s
Connections.
Create a Severe Weather Plan for your School
Objectives:
 Investigate severe weather safety
 Identify needs during a severe weather event
 Determine a classroom plan
 Compare with other classroom and school level plans
Use the Tornado Safety
(http://www.spc.noaa.gov/faq/tornado/safety.html)
information page
as resource.
Remember the big questions when putting
together a plan are what, where and when.
Only then can you make a reasonable plan.
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What type of severe weather?
Where is it going?
When is it expected to strike?
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