WW2010
University of Illinois

WW2010
 
  welcome
 
> online guides
 
  archives
 
  educational cd-rom
 
  current weather
 
  about ww2010
 
  index

Online Guides
 
  introduction
 
> meteorology
 
  remote sensing
 
  reading maps
 
  projects, activities

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

Tstorm Components
 
  introduction
 
  updrafts/downdrafts
 
  wind shear
 
> outflow phenomena
 
  wall clouds

Outflow Phenomena
 
  introduction
 
> gust fronts
 
  microbursts
 
  scud clouds, virga
 
  rain foot, dust foot

gust fronts
 
  introduction
 
  visual clues
 
> more clues

User Interface
 
  graphics
> text

NOTE: We've guessed that you're not using a client that supports colored tables and have tried to compensate. Low graphics mode looks much better on clients that do... we recommend switching to Netscape 3.0 or Microsoft Internet Explorer.
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More Clues to Gust Fronts
examining wall clouds

Still looking west from the same vantage point about 20 minutes later, the storm was moving off to the right (north) leaving a curving, weakening outflow boundary behind it. This boundary is visible as the darkest cloud base in the middle ground, arcing into the right background. Look to the right horizon. There is another rain area, and another cloud-base lowering to the south of the rain. Is this a repeat of what we have just observed? Note the subtle hint that the cloud is sloping into the rain area.

[Image: lowering near the horizon (53K)]
Photograph by: Doswell

The second storm is approaching, and the cloud lowering continues to slope into the precipitation. It is a wall cloud, exerting "pull" on the rain-cooled air and maintaining its distance from the visible precipitation shaft rather than being "pushed" away from it. We have witnessed the progression from severe multicell storm to supercell when a secondary updraft in the flanking line blossomed into a rotating updraft. This storm lasted for several hours after this stage, producing large hail and several weak tornadoes.

[Image: wall cloud maintains its distance (53K)]
Photograph by: Doswell

A final word for spotters: when watching a potential wall cloud, have patience! Don't expect a quick tornado warning when you report the wall cloud, but watch for tornadic wall cloud characteristics. The forecaster and radar operator will also be scanning the storm for tornadic signatures.



visual clues
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.

Microbursts