380 
STOUT, BLACKMER, AND WILK 
4 
STO SUPER-COOLED DROPLET 
% ICE CRYSTAL 
@ = GRAUPEL 
& HAIL (GROWING) 
40| 4 HAIL (MELTING) 
O RAIN DROP 
35 
I * + * * * * * 
° 
@ © oO 
* * * * °% * * 
BASE OF ANVIL 
HEIGHT, THOUSANDS OF FEET 
8 a 
ECHO "A" AT 0933 
15}— -~7T N 
ae 
“A 
fice 
a Oe rZ- 
ag ege 
wae sare 
AZIMUTH , DEGREES 
349° 340° 
ECHO A AT 0938 
344° are 
AZIMUTH , DEGREES 
ECHO B 
<—0933cC——| +0938 c —> 
Fic. 12—Pre-squall line hail shower 
ever, further examination of the RHI radar data 
suggests the formation of hail was aided by the 
auxiliary shower development at 342°. 
The echo configuration and apparent hail for- 
mation process is illustrated in the schematic 
in Figure 12. At 09h 33m CST, echo A was dis- 
tinguishable from 840 to 347° and sloped up- 
ward to 15,000 ft. Five minutes later, at O9h 
38m CST, echo A was entirely suspended, with 
the base at approximately 7500 ft and the top 
entering the cirrus overhang at 26,000 ft. The 
strong vertical transport ahead of the LEWP 
had carried the super-cooled droplets along the 
trajectory (1) into co-existence with the ice 
crystals in the anvil. The graupel which was 
formed in this region (2) was released to the 
lower levels and would have terminated as 
virga, except for the facet that it was in juxta- 
position with the origin of echo B. The growth 
stage of this new cell provided vertical support 
and droplets for continued particle growth (3) 
and hail formation. 
Summary and conclusions—Studies of hail 
are being made using climatological, crop-hail 
loss, radar, and volunteer observer data. No 
single type of data provides sufficient informa- 
tion to conduct a comprehensive study of hail 
formation. For example, the crop-loss data ean 
define the areal extent of damaging hail in re- 
gions where large areas of insured crops are 
located, but cannot provide information on hail 
size or concentration. The radar data ean pro- 
vide information on precipitation location, ex- 
tent, movement, and intensity, but radar is not 
capable at present of definitely distinguishing 
between rain and hail. The volunteer observer 
network data are useful in determining the size 
and concentration of hailstones and the rela- 
tionship of hail to the occurrence of rain, but 
do not permit the evaluation of the areal extent 
of hail. 
Although the primary purpose of the investi- 
gations being carried out at the Illinois State 
Water Survey is the determination of hail dis- 
tribution and radar detectibility, it is hoped 
that the preliminary case studies presented in 
this paper will contribute toward a better un- 
derstanding of the physical processes involved 
in hail formation. 
Acknowledgments—This research is partially 
supported by the Crop-Hail Insurance Actuarial 
Association and the Cambridge Air Force Re- 
search Center. 
REFERENCES 
Donatpson, R. J., Jr., Analysis of severe convective 
storms observed by radar, J. Met., 15, 44-50, 
1958. 
Dovatas, R. H., anp W. Hirscureip, Studies of 
