CLGC Soaring Weather and Data Analysis

Presentation to CLGC by Greg Chisholm, December 2000 (pdf 3.3MB)


Chicago Soaring Forecasts courtesy of CGC and NOAA-FSL

The following SkewT/LogP diagrams provide both actual and forecast soundings. The forecast soundings are derived from the actual soundings via computer simulations:

  1. TI's and SkewT/LogP diagrams: Locate the dry adiabat line for the daily forcast high (CGC is approximately 1000mb's MSL). The dry adiabat angles from lower right to upper left - colored blue, numbered in degrees F.
  2. Follow the dry adiabat up to the intersection with the sounding. The sounding is the squiggly line depicting temperature as a function of altitude - colored red. This intersection is the top of the thermal for today, given no complications, like clamp.
  3. At any altitude, the TI is the difference between the sounding temperature for that altitude and the dry adiabat temperature for that altitude.
  4. One rule of thumb is that a glider could expect to top out at TI=-3 (though many have experienced greater heights).


Advanced Digital Data Service (ADDS)

The National Weather Service's ADDS site contains a large amount of general aviation weather data. These links provide you with direct access to a number of these pages.


Dr. Jack's Blipmaps

Direct Link to Dr Jack's BLIPMAP images - Blipmap and Blipspot forecasts. This page contains 4 Blipmap images - Thermal Updraft Strength, Critical Height, Wind Speed, and Wind Direction. It also contains links to the Blipspot forecasts for the CGC location. Note: You must be a Blipmap subscriber to view all 4 Blipmap images.


Forecast by NOAA's Forcast Systems Laboratory. This link provides 5 plots from the current time. I usually select the region around the drybulb from ground (~1000mb) to 10,000 feet (e.g., place cursor to right of drybulb/1000mb intersection, depress left mouse button, drag up and to the left to above 10,000 ft line). Expected cloudbases are indicated by the following: pressure (altitude), wetbulb temp, drybulb temp, and wind direction/speed.


Additional Helpful Stuff on the Web


General Purpose Sites and Educational Information

The following is a collection of sources for the above graphics as well as some selected information sources on reading these graphics.


Created by Greg Chisholm December 1998
Modified by Rich Carlson July 2004