DISCUSSION 381 
Alberta Hailstorms, 1957, Sci. Rep. MW-27, Mc- 
Gill University, 79 pp., 1958. 
Hurr, F. A., anv 8. A. Cuananon, Jr., Hail clima- 
tology of Illinois, Rep. Invest., Ill. Water Surv., 
1959, (manuscript). 
Noten, R. H., A radar pattern associated with 
tornadoes, U. S. Weather Bureau, RADU, Kan- 
sas City, Missouri, 1959. 
Roru, R. J., Crop-Hail Insurance Actuarial As- 
sociation, Bul. Amer. Met. Soc., 36, 409-411, 
1955. 
Stout, G. E., R. H. Buacker, Jr., S. A. CHANGNON, 
Jr. and F. A. Hurr, The hail hazard in Illinois, 
Crop-Hail Insurance Actuarial Association, Chi- 
cago, Illinois, 33, 1959. 
U. S. Wearuer Bureau, Thunderstorm 
Hydromet. Rep. 5, 330 1947. 
Witk, K. E., Research concerning analysis of 
severe thunderstorms, Q. Status Rep. 1, Con- 
tract AF 19(604)—4940, Illinois State Water Sur- 
vey, 6 pp., 1959. 
rainfall, 
Discussion 
(Relating to three preceding papers by Beck- 
with; Donaldson, Chmela, and Shackford; 
and Stout, Blackmer, and Wilk.) 
Dr. W. Hitschfeld—l think Messrs. Beck- 
with, Donaldson, and Blackmer have given us 
three excellent papers in which a great deal of 
factual material was presented. So, if I may 
lead off the discussion with Donaldson’s paper, 
in Figure 10, he plotted the product of height 
and radar mtensity measured in suitable radar 
units. I think this is the kind of approach that 
could be extremely valuable in the discrimina- 
tion by radar techniques, of rain from hail, and 
possibly the recognition of tornadoes by radar. 
Mr. Beckwith showed us some. surprising 
things. The photographs of the dents that were 
produced by large size hailstones in aircraft 
at high levels are strong evidence that four- 
inch hailstones occur at such enormous levels as 
40,000 ft. This may suggest updrafts as high as 
30 or even 60 m see, depending on hailstone 
shape and density. 
Mr. Blackmer has shown us how one can use 
insurance records, which (Dr. Douglas tells 
me) are difficult to get at and analyze; and he 
has done a lot with them. I only want to sound 
a word of warning. When one comes to relating 
these insurance records with storm patterns, one 
may be in for a surprise. For instance, a 160- 
mile-long streak of damage, may turn out to 
have been caused by three or four different 
storms. 
Mr. Roy Blackmer—lI have looked a little bit 
at the radar echoes of that particular storm. 
It is a little difficult to tell just how much echo 
development was going on, because the radar 
beam was a little wide and the place where the 
echo first appeared was out toward the maxi- 
mum range of the radar. But there appears to 
be really good echo continuity along that whole 
path. 
Dr. Hitschfeld—One of the nicest features, 
by the way, is the fact that you have suggested 
in showing from what square miles you had a 
right to expect the reports, and from what 
square miles you did not. The negative infor- 
mation is Just as important as the positive. With 
the usual kind of ground observers, the negative 
information is either not available or very 
spotty but I think the way you did it gives a 
lot of credence to the continuity. 
Mr. Blackmer—With the 1959 data, we can 
put two different types of observations together: 
the volunteer observer network gives us the 
distribution of hail size and accurate time of 
oceurrence. The crop-loss data will fill in the 
gaps between those to give the exact areal 
extent. 
Dr. L. J. Battan—I am curious about the ob- 
servation of a thunderstorm that went 12,000 
ft above the troposphere. If one sets down the 
approximate equation and considers an iso- 
thermal layer, one needs very extreme vertical 
velocities, in order for a parcel to get very far 
above the tropopause. As a rule of thumb, 
Vonnegut has suggested 20 m see per kilo- 
meter of penetration. This means that the as- 
cending air must have a vertical velocity of 70 
m see or more when it passes the tropopause. 
Taking into account all the possible errors, what 
would you say was the accuracy of the height 
measurement ? 
Mr. R. J. Donaldson, Jr—Plus or minus 2000 
ft average for all of these measurements. 
Dr. Hitschfeld—How accurate is your meas- 
urement of the height of the tropopause? 
Mr. Donaldson—An arbitrary tropopause was 
taken using the point above 300 mb at which 
the lapse rate first becomes less than two degrees 
C per thousand feet. Most of the time it was 
fairly clearcut. The sounding either became iso- 
thermal, or bent backwards, indicating a nega- 
