346 
hail is common, but large hail is apparently fa- 
vored by asymmetric storm structure, with con- 
centration of the most violent convection in a 
restricted part of the storm as a whole. 
Weickmann [1953, pp. 108-109] has described a 
process which fits in very well with the notions 
above. He emphasizes that the persistence of an 
updraft column is augmented by the migration 
velocity of the storm. Weickmann likens a con- 
vective storm to a snowplow, sweeping up the un- 
stable layer ahead of it in lower levels and throw- 
ing the air out in upper levels. The amount of air 
swept up, and ascending in the updraft, is aug- 
mented when the storm is impelled to move along 
through the air mass. 
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DISCUSSION 
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Discussion 
Dr. Roscoe R. Braham, Jr.—I have had the ad- 
vantage of having heard this lecture before, and I 
think you have left out in the interest of time, one 
point that needs to be brought out in the discus- 
sion of the model; namely, the consequence of the 
dynamic dam created by the vertical transport of 
momentum and of the hydrostatic pressures being 
built up on one side. This would lead to the de- 
velopment of new clouds, as Dr. Newton suggests, 
off to the right; and in fact I have seen some of his 
analyses of hourly rainfalls tracing out this kind 
of storm system. These hourly rain patterns move 
off to the right from the path of the storm as 
analyzed from radar records. 
Mr. W. Boynton Beckwith—I would like to cast 
a vote for Dr. Newton’s theories on the basis of 
radar. Although I would not like to generalize on 
all thunderstorm echoes, I would say three- 
fourths of the thunderstorms’ echoes observed 
tend to bear out your ideas. Incidentally, we prob- 
ably have in our ten years of record, ample rain- 
