Weather

Tornadoes

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According to The Columbia Encyclopedia, a tornado is, "A dark, funnel-shaped cloud containing violently rotating air that develops below a heavy cumulonimbus cloud mass and extends toward the earth."  http://www.encyclopedia.com/printable.aspx?id=1E1:tornado

tornado.jpg
http://images.google.com/images?hl=en&q=tornadoes&um=1&ie=UTF-8&sa=N&tab=wi

April through June is known as Tornado Season.  The most occur in the midwest and has been nicknamed "tornado alley."  When a tornado is viewed on radar it has a hook shape.  When the tornado starts to descend, it is viewable because of the water droplets inside of it.  The color of a cloud.  The full diameter of the tornado is not always viewable, only where all the debrees and water droplets are.
 
"The exact processes for the formation of a funnel are not known yet.  Recent theories suggest that once a mesocyclone is underway, tornado development is related to the temperature differences across the edge of downdraft air wrapping around the mesocyclone."
 

TORNADO WATCH - This means there is a possibility of rotating wind and tornadoes
 
TORNADO WARNING - This means the NWS has detected a tornado by the doppler radar or a tornado has been spotted on the ground.

ENHANCED FUJITA SCALE

EF Scale
Class
Wind Speed
MPH
Description
EF0
weak
65-85
Gale
EF1
weak
86-110
Moderate
EF2
strong
111-135
Significant
EF3
strong
136-165
Severe

EF4

violent

166-200

Devastating

EF5

violent

>200

Incredible

waterspout.jpg
http://images.google.com/images?hl=en&q=waterspouts&um=1&ie=UTF-8&sa=N&tab=wi

WATERSPOUTS
 
You also may have heard of waterspouts.  These are tornadoes that form over water, mostly on the coast of the Gulf of Mexico.  They are usually weak.  These may eventually come on land a cause some major damage.