404 
line is markedly different and that the correla- 
tion has degenerated considerably. 
The storm of April 2, 1958, Figure 4, is an ex- 
ample of deep instability. Figure 5 shows hourly 
rain distribution. Here the lift starts close to the 
coastal ridge and there is little precipitation on 
the coastal plain, and the islands are missed com- 
pletely during long periods of the storm. This 
might be interpreted to mean that at times cy- 
clonic component of the storm produces no pre- 
cipitation while the orographic boost sets off 
substantial rain. 
There are many significant phenomena that 
repeat several times during a season, that we 
have not begun to tie down quantitatively yet. 
A distinct frequent and spectacular one consists 
INCHES 
18 20 22 24 
APRIL 2 
CLEMENT J. TODD 
of plumes of precipitation that point back to the 
high points on the ridges of the Channel Islands. 
There are silver iodide generators on the Chan- 
nel Islands, and the first year we thought that 
we had a simple observable effect of seeding. The 
plumes, however, occur when the generators are 
off as well as when they are on. Another interest- 
ing phenomenon which has appeared several 
times is a plume of precipitation that points back 
to the channel between the two main islands, ap- 
parently identical to what Fujiwara [1958] has 
observed in Japan. 
Precipitation mechanism—The possibility of 
discriminating between the condensation-coales- 
cence and the ice-precipitation processes from 
ground observations seems good. As reported by 
SAN RAFAEL RIOGE 
SANTA YNEZ VALLEY 
COASTAL RIDGE 
ISLANDS 
04 06 os 10 12 14 
APRIL 3,1958 
Fre. 5—Hourly rainfall averaged over orographic regions for the typical convective storm of April 
2-3, 1958 
