WW2010
University of Illinois

WW2010
 
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> archives
 
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Archives
 
> case studies

Case Studies
 
  introduction
 
  veterans day snow
 
  hurricane andrew
 
> 4/19 il tornadoes
 
  superstorm '93

4/19 IL Tornadoes
 
  headlines
 
  from the chase
 
  the damage
 
  how it happened
 
> nexrad close-ups
 
  data and images

NEXRad Close Ups
 
  introduction
 
  jacksonville
 
  springfield
 
  decatur
 
  monticello
 
  urbana
 
  ogden
 
> using velocities

User Interface
 
  graphics
> text

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Using NEXRad Velocities
looking for velocity couplets

Doppler radar is a useful in finding the rotating winds of mesocyclones. A mesocyclone is a column of spinning air 5 to 10 kilometers across and a precursor to the development of a tornado.

[Image: (24K)]

Roughly 95 percent of all mesocyclones produce severe weather while approximately 30 percent result in tornadoes. Mesocyclones have a distinct signature on Doppler radar images, for example in the panel above. This image displays a mesocyclone associated with the tornadic supercell that moved through Ogden, Illinois around 9:00 PM CDT on April 19th.

The mesocyclone is shown here as the abrupt change in pixel color from red to blue, indicating a sharp change in wind direction over a very short distance. If a tornado develops out of a particular mesocyclone, the time between the initial mesocyclone identification and a tornado touchdown is roughly 20 minutes.


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.