BEHAVIOR PATTERNS OF NEW ENGLAND HAILSTORMS 
365 
TaBLE 3—T'otal precipitation mass in hailstorms (assuming all radar echo is from 1-cm hail) 
P J 
Storm date and type 
July 30, 1957 
‘first echo’ hailstorm 
July 11, 1958 
hailstorm with tornadoes 
First Echo, 15h38m-40m 
Soon after first echo, 15h45m-16h02m 
(first hail at 16h01m) 
Developing, 15h03m—05m 
Stage and time Mass 
gm 
3 X 10° 
3 X 10° 
6X 104 
Mature, 15h38m—43m (first tornado near 15h30m) 4 x 10! 
Mature, 16h06m-—18m (two tornadoes near 16h00m) 5 1022 
Mature, 16h42m~-17h02m (lull in severe weather) 4 xX 10! 
Peak maturity, 17h80m-39m (final, most damaging <0 
tornado 17h15m-30m) 
TaBLE 4—Tropopause penetration by July 11, 1958 tornado storm (tropopause height = 38,000 ft) 
Measurement time 
Echo top height 
Mean echo area, 38 to 44 Kk ft 
Mean echo area, 44 K ft to top 
Echo volume in stratosphere 
Total penetration energy 
15h31m 16h03m 
51,000 ft 49,000 ft 
310 km? 2000 km? 
110 km? 570 km? 
800 km# 4500 km? 
1.7 X 10% ergs 6.3 X 107! ergs 
attributed to l-em hail would be returned by 
three times the mass concentration of 8-mm water 
drops, about 3 the mass concentration of 4-em 
hail, and somewhere between 43 and 4 of the 
mass concentration of a 1l-em particle composed 
of a mixture of ice and water in equal parts. 
With these limitations in mind, the total mass 
of precipitation, assuming it to consist entirely 
of 1-em hail, was added up for the two storms 
under consideration and is listed in Table 3. 
Echo areas near and above the tropopause 
were measured with reasonable accuracy at two 
times in the tornado storm of July 11, 1958. In 
both cases the areas above the tropopause de- 
creased with height, at first im a linear fashion 
and then more rapidly near the echo top. How- 
ever, the second measurement, about one-half 
hour later than the first, showed much larger 
echo areas penetrating above the tropopause 
level. The echo volume in the stratosphere in- 
creased more than five times, and the energy re- 
quired for penetration increased by more than a 
factor of three (see Table 4). The penetration 
energies were computed in two steps because the 
specific negative energy from the tropopause at 
38,000 ft up to 44,000 ft was relatively small, but 
increased rapidly above 44,000 ft in a strong 
temperature inversion. 
Malkus [1959] has demonstrated the critical 
role of element size in the penetration of Cumulo- 
nimbus towers; the lower entrainment rate for 
the large element size inhibits the dilution of the 
‘protected core.’ The echo areas of this tornado 
storm at the tropopause are much larger than the 
element areas reported by Malkus for clouds 
reaching 50,000 ft in Hurricane Daisy of 1958. 
However, the penetrations above the tropopause 
were somewhat greater in the case of the tornado 
storm. 
The rapid increase in echo volume above the 
tropopause and in the computed total energy re- 
quired for penetration of the tropopause, along 
with a shght decrease in echo top height, sug- 
gests a progressive modification of the lower 
stratosphere in such a manner that the actual 
penetration energy does not increase so markedly 
with time, or perhaps even decreases. The mixing 
of the early storm tops with the lower strato- 
sphere would moisten and cool the region so that 
subsequent penetrations would require less en- 
ergy. The vertical exchange of momentum sup- 
ported by the strong updrafts necessary for pene- 
tration of the tropopause by particles large 
enough to give a radar echo would tend to main- 
tain and enhance the modified region above the 
main body of the storm. In effect, the tropopause 
would seem to be bulging upward in the vicinity 
of the storm, though the authors have no knowl- 
edge of direct measurements of temperature or 
humidity which would confirm or deny this pic- 
ture. 
Characteristics of New England hail—During 
