Regional And Mesoscale Meteorology Team
Daily Satellite Discussion
Friday June 20, 1997
The area of interest is in southeast Wyoming. On this day, a tornado warning was issued for persons living east of Cheyenne. Notice how different the thunderstorm appears in the two GOES images. The most noticeable feature was the location of the eastern edge of the cirrus anvil. In GOES-8 image, the leading edge of the anvil "appeared" west of the Nebraska border while from GOES-9 it "appeared" over extreme western Nebraska. The shape of storm top was also different in the two images. From GOES-8, the top took on a more elliptical form while in GOES-9 the shape was more rectangular. The shift in location and change in shape was due to parallax.
One may become comfortable when viewing images and thinking that cloud elements are located directly above points on the land when in fact they may be located some distance to the right or left. The corresponding land location directly below the leading edge of the anvil of the storm in southeast Wyoming in GOES-8 was some 16.0 km to the southeast.
I would like to thank Carol Vaughn for providing me with the satellite images and for computing the parallax distances.
Louie Grasso