Some Behavior Patterns of New England Hailstorms 
Raueu J. Donaupson, Jr., AND ALBERT C. CHMELA 
Geophysics Research Directorate, Air Force Cambridge Research Center, 
Bedford, Massachusetts 
AND 
CHARLES REEVE SHACKFORD 
Allied Research Associates, Inc., Boston, Massachusetts 
Abstract—Radar measurements of New England thunderstorms have been com- 
bined with reports furnished by cooperative observers during three years. Echo tops in 
storms releasing hail of less than %4-inch diameter were higher, colder, and penetrated 
the tropopause more often than tops of rain thunderstorms. The differences are even 
more striking for storms with large hail (%4-inch or larger) compared with the other 
two categories. Extreme tropopause penetrations of 10,000 to 15,000 ft occurred on five 
days, of which all but one were tornado days. 
A study was made of the histories of 20 hailstorms. Ten of them dropped hail for 
long periods of time (hail repeaters), the others for less than 20 min and at only one or 
two locations. All cases of severe damaging winds and tornadoes occurred with the 
hail repeaters. Within a wide scatter, both echo tops and maximum intensities in the 
hail repeaters attained higher peaks and remained high for longer periods of time than 
in the single hail producers. Hail locations in all storms exhibited a slight tendency to 
appear in the right, rear quadrant of the storm, with the larger hail sizes located to the 
right of the smaller hail, facmg downstream. 
Echo areas of various intensities as a function of height were measured in two hail- 
storms, one just getting under way and the other a well-developed producer of several 
tornadoes. Computations are made of hail-mass concentration versus height at various 
times in the two storms, assuming the radar echo is scattered from 1-cm ice spheres. 
Mean 1-cm hail concentrations in the tornado storm, averaged over the total echo area 
at the height of the most intense echo, varied from 0.3 to 1.3 g/m*, but the maximum 
concentrations in the echo core ranged from 9 to 170 g/m*, subject to a possible over- 
estimate by a factor of 5 due to an unresolved radar calibration error. During two ob- 
servations of echo tops penetrating the tropopause, the echo volume above the tropo- 
pause increased rapidly with time, suggesting a progressive modification of the lower 
stratosphere above the storm. 
Hailstone information furnished by cooperative observers is summarized. Median 
values are: maximum diameter, 7 mm; max/min size ratio in a hailfall, 2; number 
concentration, 0.1/m*; hailfall duration, 3-4 minutes; hailfall started four minutes after 
heavy rain began. About 75% of hail shapes were divided between spheres and oblates. 
Introduction—Thunderstorms have been stud- 
ied in southern New England during 1956 through 
1958 by a combination of CPS-9 radar observa- 
tions taken from Blue Hill, Milton, Massachu- 
setts, and storm reports received from a network 
of cooperating observers. This paper is a descrip- 
tion of some of the characteristics of hailstorms 
observed during the three years of the investiga- 
tion. 
The CPS-9 radar has a 1° conical beam which 
can be set at any desired elevation angle. A series 
of antenna rotations about a vertical axis (PPI 
354 
scan) with successive increases in elevation angle 
causes the beam to sweep out a volume defined 
by a cone of revolution with vertex centered at 
the radar position. All parts of thunderstorms 
(except those within 25 mi) can be observed con- 
veniently by this means. The height of an echo 
volume is given by its range and elevation angle. 
The heights of echoes within 25 mi were usually 
measured by means of an RHI sean (a rapid ver- 
tical slice from near-zenith to horizon, at fixed 
azimuth). Echo intensity can be determined by 
means of a calibrated receiver gain control. Er- 
