STOUT, BLACKMER, AND WILK 
PERCENT OF CROP 
DESTROYED 
O 0-25 
N 25-50 
M 50-75 
: | 
v ae sf 
“  CHAMPAIGN-URBANA 
od 
Fra. 7—Hail intensity on August 9, 1954 
error. First, losses to a single crop may be used 
in detailed studies; second, periods when all 
crops are equally susceptible to hail may be 
studied. Fortunately, one of the major crops 
in Illinois, soybeans, does not vary appreciably 
in susceptibility to hail during its life history. 
To show that two crops may be equally sus- 
ceptible, the distribution of various rates of 
damage were compared for corn and soybeans 
for the storm of August 7, 1953. This compari- 
son showed no significant difference in rates of 
damage to the two crops per unit area. 
Currently, a study is being made to compare 
hail intensity with slope of terrain over which 
the storm is moving. This study is not. suffi- 
ciently advanced to report at this time. One of 
the limitations mm studying hail intensity using 
crop-loss data is the lack of information about 
the size and concentration of the hailstones. 
Identical crop damage could result from many 
combinations of hailstone size and concentra- 
tion. It is at this point that the networks of 
volunteer observers become necessary. 
Analysis of radar and network data—A net- 
work of volunteer observers was established in 
central Illinois in the summer of 1958, under 
AFCRC sponsorship (AF Contract 19(604)- 
4940, The Determination of Techniques for 
Radar Identification of Severe Thunderstorms). 
Approximately 1000 volunteer observers, lo- 
cated within a 380-county area and 100-mile 
range of the radar, furnished detailed reports 
concerning the time of occurrence, size, and 
concentration of hail, as well as reports of dam- 
aging wind, hghtning, and heavy rain. Exami- 
nation of these data in conjunction with PPI 
(CPS-9) and RHI (TPS-10) radar data yielded 
several enlightening facts concerning hailstorm 
formation. 
Mid-tropospheric jet penetration—PPI radar 
display of intense pre-cold frontal squall line 
activity often exhibits major distortions, or 
bulges, indicative of zonal acceleration within 
