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

User Interface
 
  graphics
> text

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Scud Clouds and Virga
minimal precipitation at the surface

Scud clouds are low, detached clouds caught in the outflow beneath the thunderstorm. As cold air first reaches the ground, it lifts relatively warm air, resulting in saturation through ascent. Thus, the presence of sub-thunderstorm base scud clouds almost always indicates the presence of outflow.

[Image: scud clouds (58K)]
Photograph by Doswell

This is a dissipating multicell anvil cloud, looking northeast, late in the afternoon near Fort Morgan, Colorado. Note the lack of precipitation beneath the dissipating storm cell, except for the white virga streak behind the tree line.

[Image: (56K)]
Photograph by Moller

The area close to this virga could be quite dangerous for low-level aircraft operations. Microbursts that occur with virga are aptly called dry microbursts, even though a spattering of raindrops may reach the surface.



Microbursts
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.

rain foot, dust foot