HAILSTORM STRUCTURE VIEWED FROM 382,000 FEET oe 
strong shear between these flows spawns eddies, 
some of which develop sufficiently to show up as 
a long vortex such as the one visible on Figure 
5. Figure 7 is an enlargement of the region in 
which the vortex is visible. 
Close inspection of the ground shading in 
Figures 2 and 5 reveals the pattern of rain cover- 
age from the nearby storm. The darker ground 
leading to the left of the storm is the ground wet 
by the heavy rain and hail. The spots of white 
on the upper side of this dark area are patches 
of hail left by the storm. According to W. B. 
Beckwith (private communication) hail on the 
ground that falls with little rain will show well 
from the air but when accompanied by heavy 
rain it will be washed into the vegetation and 
gullies and will not show. Hail, therefore, could 
have fallen throughout the precipitation area but 
only show on the ground where it separated from 
the other hydrometeors, descending along a dif- 
ferent trajectory because of its greater fall ve- 
locity. 
Many of the features discussed above are 
SCALE 
Gaamtmem eo os 
10 
stat. mi 
+0 == WHITE HAIL PILES ON GROUND 
<> © AREA OF WET GROUND 
Laas 
Oo <VORTEX 
| Hes il 
a ‘— CENTER OF RADAR ECHOES AND TIME 
(WB BECKWITH UNITED AIRLINES DEN) 
E05] <— HAIL, SNOW, AND RAIN REGION 
CHEYENNE WYO. 
MARBLE Ss shoe) 
a 
HAIL 1305 
Oo 
—_ 
mapped on Figure 8 through the use of the 
Canadian grid technique on single photographs 
and by triangulation using several photographs. 
The similarity im size, shape, and spacing of 
these storms is striking. The anvils appear to 
spread off in the down shear direction, extending 
for about 100 mi. The motion of the storm mass 
itself has been measured as along the direction 
of the anvil and at the low velocity of 21 knots, 
or a speed equivalent to the speed of the ambient 
air (Scotts Bluff raob) at the cloud base. This 
measurement was made utilizing all the time 
fixes indicated except the 1345 radar position. 
The radar positions were obtained from W. B. 
Beckwith (private communication). Additional 
fixes were obtained from surface observations at 
Cheyenne, noted on Figure 8, and Akron, Colo- 
rado, where the storm was observed passing north 
of the town at 17h00m. The aircraft photograph 
also gives a fix at 15h00m. The fix used from 
the photographs was placed five miles east of 
the indicated vortex position. The speeds caleu- 
lated from the six fixes were in close agreement, 
q 
GREELY COLO. wo. a1 
FLIGHT PATH 
AND PHOTO NOS. 
Fie. 8—Cloud map of hail and thunderstorms from areal photographs, 
September 11, 1958, 15h 00m MST, from T-11 oblique photos from AFCRC 
C-130 aircraft 
