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

Modeling
 
  introduction
 
  supercells
 
  convective lines
 
> forecasting

Forecasting
 
  introduction
 
  forecast matrix
 
> parameters
 
  ncsa access article

Parameters
 
> stability
 
  wind shear
 
  cape

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.
.
Stability

Storms developing in one environment can be different in character than those developing in another. Modelers can alter the stability of the atmosphere in which they simulate storms by changing the vertical distribution of temperature and moisture.

Thunderstorms develop when surface and low level air is allowed to rise without restriction into the upper troposphere. If air rises in an environment without restriction, the environment is said to be unstable. This means that stability is simply the resistance the atmosphere imposes on rising (or sinking) air.

Stable Environments
Air temperature in the atmosphere generally decreases with height. However, when low level air rises, it cools at a rate that is often different from the air's surrounding environment. If, as it rises, the low level air becomes colder than its environment, it would be more dense than the environment and fall back toward its original level. This is a stable environment.

The only way air can rise in a stable environment is for a mechanical force such as a front to lift it. [Image: (23K)]
Unstable Environments
If, however, the rising air cools at a slower rate than the surrounding atmosphere, it will be warmer (and less dense) than its surroundings. Here, the rising air would continue rise.

[Image: (22K)] The larger the temperature difference between the rising air and the environment, the more buoyant the rising air is. The more buoyant the air is, the faster it can rise, and the more severe the thunderstorm can become.

Sometimes, the environment is stable near the ground and must be forced to rise into unstable air by a front or other mechanism.



Forecasting
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.

wind shear