362 
LOW ALTITUDE 
ECHO CORE << 
x (Zp max) 
MILES 
DONALDSON, CHMELA, AND SHACKFORD 
HAIL DIAMETER : 
DIRECTION OF ECHO CORE 
Fic. 11—Position of leading edge of hail relative to low-altitude echo 
core 
Taste 2—Mean hail locations relative to low altitude echo core 
Normal to echo core path 
Along echo core path 
Maximum hail diameter 
inch 
D<% 
stream) 
y%<D< &% 0 mi (on path) 
D> 0.9 mi to right 
All hail 
1.2 mi to left (facing down- 
0.48 mi to right (84 cases) 
1.7 mi behind 
1.2 mi ahead 
0.4 mi behind 
0.16 mi ahead (25 cases) 
the timing was in doubt but the location exact; 
for these cases the hail position could be deter- 
mined normal to the path of the echo core but not 
along the path. There was similar scatter in posi- 
tion, but in over half of these cases the hail fell 
two miles or less to the right or left of the echo 
core path, or exactly on the path. Table 2 sum- 
marizes the mean hail locations for various hail 
sizes. It shows a progressive tendency for the 
larger hail to be located toward the right-hand 
side of the core path, in support of the model pro- 
posed by Newton [1959]. Since these locations are 
for the forward edge of the hailfall, which has a 
median duration of three to four minutes (see 
later under Characteristics of New England hail), 
the hail path tends to lag the echo core. Thus, the 
right rear quadrant of the storm (with respect to 
the echo core) shows a weak tendency to claim 
the greater part of hail. 
Hailstorm echo areas—The echo areas at var- 
ious receiver-gain settings and elevation angles 
were traced in two of the storms, one in which a 
first echo was detected (Storm 10) and the other, 
Storm 19, a producer of several tornadoes. Fig- 
ure 12 is an example for Storm 10, for three gain 
settings. 
The areas enclosed by various values of equiv- 
alent reflectivity factor Z, as a function of height, 
were computed for both storms at different times 
in their history. The areal heights were obtained 
simply from the height of the echo core at each 
antenna elevation angle. Similarly, the range of 
the echo core at each height was adopted as an 
average range for purposes of computing the 
