University of Illinois

> online guides
  educational cd-rom
  current weather
  about ww2010

Online Guides
  remote sensing
> reading maps
  projects, activities

Reading Maps
  utc conversions
  temp conversions
  surface obs
> surface maps
  upper air obs

Surafce Maps
  obs, isobars, radar
  obs, isobars, ir sat
  temp contours
  temperatures, winds
  dew point reports
  dew points, winds
  24 hour totals
> analysis pairs

Analysis Pairs
  press & temp
  dew point
  mixing ratio
> moist. convergence
  temp. advection
  dew point advect
  3hr dew pt & wind
  3hr temp & wind
  3hr press & wind

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.
Moisture Convergence and Wind Vectors
surface analysis pairs

Example Moisture Convergence and Wind Vectors

This panel depicts surface wind vectors and moisture convergence. This chart is most useful in locating areas where thunderstorms will develop.

The solid red contours represent moisture convergence. Moisture convergence has a contour interval of 10 g/kg per second. The chart above is usually factored by 1000 to make the values easier to contour. Moisture convergence is a very important tool in forecasting the development of thunderstorms in the short term. Two of the primary factors in developing thunderstorms are a supply of moisture and low-level convergence. These two quantities are combined in this chart to give you moisture convergence. Surface moisture convergence generally precedes the development of thunderstorms by a few hours.

The blue arrows represent wind vectors. Wind vectors point in the direction the wind is blowing, and the longer the wind vector, the stronger the wind. From the map above you can easily find warm, cold, occluded, and stationary fronts. Fronts are usually located in areas were winds come together and change direction. Low and high pressure systems can also be located from the map above. Winds around low pressure move counter-clockwise (cyclonic) and in towards the center. While winds around high pressure move clockwise (anticylonic) and out away from the center.

The above example image is from April 19, 1996 taken at 4pm in the afternoon. From approximately 6-10pm 30 tornadoes ravaged the state of Illinois. Moisture convergence was a very important tool that day in forecasting the initiation of severe thunderstorms.

mixing ratio
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.

temp. advection