Oo 20 40 60 80 100 
NAUT MI 
Fic. 4—Rainfall near Fort Wayne, Indiana, in 
hour ending 20h00m CST, April 28, 1951; outer 
isohyet, 0.01 inch, then 0.20, 0.50 (hatched inside), 
and 1.00 inch 
Fig. 5—Winds in Fort Wayne vicinity, April 28, 
1951, at 10,000-ft level (light symbols, full barb 10 
kt) and vector shear 4000-18,000 ft (heavy ar- 
rows); solid lines, 700-mb contours; dashed, 850- 
500 mb thickness (hundreds of feet) 
front of a wave cyclone, with SSW-SW winds in 
the lowest few thousand feet, and winds from 
W in the upper troposphere. Although no upper- 
wind observation is available for Fort Wayne, the 
vertical shear vectors at surrounding stations 
(Fig. 5) clearly suggest that the hail occurred on 
the downshear flank of the rainstorm. Successive 
rainfall maps showed movement of the rain area 
as a whole toward ESE, somewhat to right of the 
upper winds. 
The second example is shown in Figure 6 from 
Hamilton [1958], who gives a detailed description 
of the use of radar in tracking the storm and in 
identifying the hail. First echo appeared at A at 
14h40m CST; hail was first apparent at B. Large 
hail (up to 2-inch diameter, some larger) and high 
winds occurred intermittently along a narrow 
track 130 mi long, ending near Bremond prob- 
CHESTER W. NEWTON 
ably around 18h380m CST. A tornado occurred at 
Midlothian (C). The track of large hail was con- 
fined to the right side of the storm, which pro- 
duced small hail along with the extensive heavy 
rain. 
It is not possible to reconstruct the exact con- 
ditions in the neighborhood of the storm, but as 
far as can be determined, the Fort Worth winds of 
12h00m CST (inset, Fig. 6) are nearly representa- 
tive. By 18h00m CST, winds were W to WNW 
in lower levels. Hamilton quotes a radar report 
stating that echo movements (individual cells?) 
were from west, an agreement with the mean 
winds in the cloud layer in Figure 6, inset. 
The Fort Worth hodograph, as well as the 850- 
and 300-mb wind charts (Fig. 7) shows strong 
veering with elevation. According to the earlier 
conclusions, pronounced building of new storms 
should be expected on the SSE side of the rain- 
storm at a given time, with marked deviation of 
the storm track to right of the mean winds. The 
movement of the rainstorm is thus qualitatively 
in agreement with expectations, although the de- 
viation to right is stronger than might be ex- 
pected. 
Without a detailed analysis on the scale of the 
storm itself, it is not possible to give a reason for 
this excessive deviation. In an earlier study [New- 
ton and Katz, 1958] it was found that rainstorms 
moved on the average 7 knots slower than, and 
25° to right of, the 850-500 mb mean winds in the 
cases concerned. Individual storms, however, ap- 
peared to deviate up to 20-30 knots vector veloc- 
ity from this mean behavior. 
Such aberrations are to be expected in a phe- 
nomenon so complicated as a large thunderstorm, 
where many different processes are at work. The 
above discussion is obviously oversimplified; for 
example, a low-level outflow, assumed to radiate 
uniformly outward from storm center, has been 
added to a mean in-cloud velocity based on the 
ambient winds, in arriving at the relative velocity 
at a given point on the storm boundary [Newton 
and Newton, 1959]. 
Very likely other hydrodynamic effects are 
present which modify the simple conclusions here. 
Byers [1942] was the first to give a systematic 
description of the movement of thunderstorm 
paths to right of the winds. His observations sug- 
gested a cyclonic rotation within individual 
storms. Byers explained the storm movements on 
the basis of the rotor principle (a counterclock- 
wise-rotating cylinder propels itself to right of the 
current in which it is imbedded). 
On the basis of about 30 synoptic situations 
