° 10 20 30 40 30 
Stotute Miles 
Contour Interval 200011 7 
TUCSON 
ao \ 
a 
% 
“us 
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os 
Se 
we ice 8, 
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UMACACOR 9 
s %, 
7-20-56 
EcHo Groups 
Fic. 2—Plan view of echo areas on July 20, 1956; areas represent echoes detected on a single 360° 
azimuth sean at approximately one-hour intervals, time identification to nearest whole or half hour, 
mst; to simplify the presentation a single outline encloses groups of closely spaced echoes, and, occa- 
sionally, groups of echoes on consecutive hours when they occupied essentially the same region; on the 
base chart are shown the 3000 ft contour and elevations greater than 5000 ft msl (shaded areas); dis- 
tance scale, in miles, is shown to left of center 
80 
