WW2010
University of Illinois

WW2010
 
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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

Clouds, Precipitation
 
  introduction
 
  mechanisms
 
  precip processes
 
  high level clouds
 
  mid level clouds
 
  low level clouds
 
> vertically developed
 
  other cloud types

Vertically Developed
 
  fair wx cumulus
 
> cumulonimbus

User Interface
 
  graphics
> text

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Cumulonimbus Clouds
towers reaching high into the troposphere

Cumulonimbus clouds are much larger and more vertically developed than fair weather cumulus. They can exist as individual towers or form a line of towers called a squall line. Fueled by vigorous convective updrafts (sometimes in excess 50 miles/hour), the tops of cumulonimbus clouds can easily reach 39000 feet (12000 meters) or higher.

[Image: example of cumulonimbus clouds (74K)]


The lower portion of the cloud consists mostly of water droplets while at the cloud top, where temperatures are well below 0 degrees Celsius, there are primarily ice crystals. Under favorable atmospheric conditions, what may initially appear as harmless fair weather cumulus clouds can quickly develop into large cumulonimbus clouds. Occasionally, these clouds grow into powerful thunderstorms known as supercells.

[Image: example of supercell (77K)]


Supercells are large thunderstorms whose updrafts and downdrafts are so closely in balance that such a storm can have a lifetime of several hours. Fueled by intense updrafts (occasionally reaching 90 m.p.h.), supercells can produce large hail, damaging winds, and tornadoes. Supercells are typically characterized by strong vertical shear and steep lapse rates. Supercells tend to develop during the afternoon and the early hours, when the effects of heating by the sun are strongest.

[Image: approaching cumulonimbus clouds at sunset (69K)]


A line of approaching thunderstorms at sunset might resemble something like the picture above. The sun setting behind this developing cumulonimbus tower clearly reveals the distinct cloud edges that mark the extent of the rising air.


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.