Illustrated tornado from the book The Wizard of Oz
© W. R. Wright, Piglet Press Inc. (www.halcyon.com/piglet/)
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Tornadoes are very destructive, so it's important to know when one may
form so you can take shelter. Forecastors at the National Weather
Service are always on the lookout for developing storms. Even though
nobody knows how tornadoes form, they do know
the conditions when they are most likely to form. When the conditions
exist, the Storm Prediction Center in Norman, Oklahoma, issues a tornado
watch. The watches usually last from four to six hours and usually cover
a box from 20,000 to 40,000 square miles.
The local storm
spotter network activates when a watch is issued. The spotters are
trained to notice tornadoes as they form. If a spotter sees a tornado,
the local Weather Service office will issue a tornado warning for the
county or counties near the tornado. They can also issue warnings based
on radar images.
There are certain radar echos that are associated with tornadoes and they
use the echos to forecast when a
tornado will form.
You will hear about warnings issued for your county or parish through
different ways. Many cities have tornado sirens which sound when a
warning is issued. Also, the new Emergency Alert System
can notify people over radio and television even if their radios and
televisions are turned off. Another aspect of the EAS is it allows for
site-specific warnings. If you live in one place you'll only hear
warnings for you, not for some other place in the station's viewing or
listening area.
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