University of Illinois

> online guides
  educational cd-rom
  current weather
  about ww2010

Online Guides
> meteorology
  remote sensing
  reading maps
  projects, activities

  air masses, fronts
  clouds, precipitation
  el nino
  forces, winds
  hydrologic cycle
  light, optics
> midlatitude cyclones
  severe storms
  weather forecasting

Midlatitude Cyclones
  associated winds
  air masses
  on satellite images
> upper air features

Upper Air Features
  geopotential height
  wave amplification
> rising motion
  steering level
  jet stream
  jet streaks
  vertical motions
  mid-level moisture
  wind vectors

User Interface
> 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.
Rising Motion and Surface Pressure Falls
in response to warm and cold advections

Warm and cold advection influence vertical air motion. Warm advection results in rising motion which leads to falling pressures at the surface, while cold advection leads to sinking motion, causing pressures to rise at the surface. The sequence of surface maps below show the surface pressure fields (isobars) that resulted from the warm and cold advection patterns at 850 mb.

[Image: (53K)]

The top map shows an area of low pressure over the northwestern United States and an area of high pressure over the eastern U.S. 12 hours later, there is a noticeable decrease in pressure from Texas to Illinois (region of strongest warm advection at 850 mb) while surface pressures increased in regions where the strongest 850 mb cold advection was occurring.

[Image: (49K)]

A cyclone at the surface that moves under an area of warm advection at 850mb is likely to deepen. For this reason, systems at the surface will tend to "phase lock" with systems aloft, and they will propagate more or less together.

wave amplification
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.

steering level