WW2010
University of Illinois

WW2010
 
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> online guides
 
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Online Guides
 
  introduction
 
> meteorology
 
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Meteorology
 
  introduction
 
  air masses, fronts
 
  clouds, precipitation
 
  el nino
 
  forces, winds
 
  hurricanes
 
  hydrologic cycle
 
  light, optics
 
  midlatitude cyclones
 
> severe storms
 
  weather forecasting

Severe Storms
 
  introduction
 
> dangers of t-storms
 
  types of t-storms
 
  tstorm components
 
  tornadoes
 
  modeling

Dangers of T-storms
 
  lightning
 
  flash floods, hail
 
  outflow
 
  downbursts
 
> tornadoes

User Interface
 
  graphics
> text

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Tornadoes
violently rotating columns of air

The last severe weather element is the tornado. Defined as a violently rotating column of air in contact with the ground and pendent from a cumulonimbus cloud, tornadoes are capable of inflicting extreme damage.

[Image: weak tornado (49K)]
Photograph by: Marshall

They can be categorized as "weak", "strong", and "violent"; with weak tornadoes often having a thin, rope-like appearance, as exhibited by this tornado near Dawn, Texas (looking west from about 1 mile). About 7 in 10 tornadoes are weak, with rotating wind speeds no greater than about 110 MPH.

The typical strong tornado often has what is popularly considered a more "classic" funnel-shaped cloud associated with the whirling updraft. Rotating wind speeds vary from 110 to 200 MPH.

[Image: strong tornado (68K)]
Photograph by: NSSL

Nearly 3 in 10 tornadoes are strong, such as this twister on the plains of North Dakota. Looking northeast, note the spiraling inflow cloud, probably a tail cloud, feeding into the tornado. An important safety consideration is that weak and strong tornadoes, by definition, do not level well-built homes. Thus, a secure home will offer shelter from almost 100 percent of all direct tornado strikes.

Only violent tornadoes are capable of leveling a well-anchored, solidly constructed home. Fortunately, less than 2 percent of all tornadoes reach the 200+ MPH violent category. Furthermore, most violent tornadoes only produce home-leveling damage within a very small portion of their overall damage swath. Less than 5 percent of the 5,000 affected homes in Wichita Falls, Texas were leveled by this massive 1979 tornado. (Looking south from about 5 miles).

[Image: violent tornado (79K)]
Photograph by: IDR

Note the huge, circular wall cloud above the tornado. This feature is probably close both in size and location to the parent rotating updraft (called a mesocyclone) which has spawned the violent tornado. Strong and violent tornadoes are usually associated with storms containing mesocyclones.



downbursts
Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

Types of T-storms