Figure 2: (a) 500 mb analysis and upper air observations, (b) 850 mb analysis and upper air observations valid at 0000 UTC, 9 May 2003. The red-shaded circle denotes the position of a short-wave trough. Heights are shown as black contours (in decameters), temperature is shown by dashed red contours, and dewpoint temperatures greater than 8 degrees celsius are contoured in green. Note also the 850 mb 50 knot wind observation at Dallas/Fort Worth (image from http://www.spc.noaa.gov/).