HAIL STUDIES RELATING TO CLOUD 
PPI 
(00 MILE RANGE 
342° 
PHYSICS 
RHI 
349° AZIMUTH 
RHI 
AZIMUTH 
Fia. 10—Line echo wave pattern, August 8, 1958 
08 FREEZING 
LEVEL 12,200 FT. 
HEIGHT , THOUSANDS OF FEET 
MILLIBARS 
7 
/ 
if TEMPERATURE 
5) 7 
7 
a? 4: 
a 
08 FREEZING 
PRESSURE , 
O600 CST PEORIA RAOB 
1030 CST RW- 4 INCH HAIL 
1200 CST PEORIA RAOB 
Fic. 11—Profile of a pre-squall line hail shower 
observations confirmed the stationary front po- 
sition in northern Illinois at 06h 00m CST and 
12h00m CST. The single wind maxima of 299°, 
62 knots, occurred at 16,000 ft. 
Pre-squall line hail shower occurrence—The 
PPI radar display for August 7, 1958, shown in 
Figure 10 indicates a less continuous line than 
that associated with the LEWP on July 27, 
1958. It is apparent that further loss of line 
continuity results in the LEWP becoming am- 
biguous, as is highly probable in the case of 
isolated radar echoes associated with 
weather. 
Most of the hail occurred simultaneously with 
the heavy rain associated with the principal 
thunderstorm cells. However, one detailed re- 
port was received of hail falling in advance of 
the disturbance. An examination of the RHI 
radar data disclosed a unique echo over this 
severe 
location. The echo at 349°, as shown in Figure 
10, exhibited distinct streamers which 
gested the existence of hail shafts. The only 
other echo in proximity was a suspended cell 
at 342°. Analysis of the Peoria rawinsonde data 
for 06h 00m CST and 12h 00m CST provided 
the general airmass temperature and moisture 
distributions south and north of the LEWP de- 
velopment. The profile in Figure 11 shows the 
streamers becoming continuous near the minus 
five-degree centigrade level, diffusing, and losing 
their identity near the wet-bulb freezing level. 
The echo depth decreased below the convective 
condensation level suggesting that limited evap- 
oration was occurring. The surface observation 
indicated very light rain associated with one- 
fourth inch hail. 
It was initially assumed that the hail was 
thrown out from the main thunderstorm. How- 
sug- 
