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

Tornadoes
 
  introduction
 
> useful diagrams
 
  low-level flow
 
  evolution (photos)
 
  cyclic storms

Useful Diagrams
 
  tornadic supercell
 
> mesocyclone
 
  storm evolution

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.
.
Focusing on the Mesocyclone
of a tornadic supercell

To illustrate these points further, let us imagine that radar and spotters detect a possible supercell that is approaching a community. The spotter group's net controller first considers that the spotters must concentrate on that portion of the supercell which is most important: The quadrant with the updraft/downdraft interface.

If we center a coordinate axis and grid system on the storm's radar centroid, the "action" area typically is in the southwest quadrant as seen in this storm's horizontal cross-sectional view. Warm, ground-relative inflow winds are depicted by orange arrows and cold outflow is in blue, with the longest arrows suggestive of the strongest winds. The gust front is depicted by the thick, blue line, and the mesocyclone by the "L", or low pressure center in the gust front wave.

[Image: schematic of mesocyclone (55K)]

Note the storm motion vectors. Although a majority of these supercells move northeast or east, a significant number move southeast. Therefore, the heaviest precipitation usually either precedes the tornado (northeast movement) or falls immediately north of the tornado track (southeast movement), although brief bursts of large hail and/or rain often occur with the tornado.

Supercells frequently move to the "right" of non-supercell storms, even to the extreme of moving southeast on a day when winds aloft all blow from the southwest. Vigorous development on the south side of the main updraft apparently causes this rightward storm motion. Let us now concentrate on the storm flank where the most violent weather will occur.



tornadic supercell
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.

storm evolution