WMOD00284

• Applicant: Thompson, J.R., G.W. Wilderson, and D.A. Griffith, North American Weather Consultants
• Sponsor Name: USBR
• Title: Cloud Seeding Data Collection, and Analysis Assoc. with the Colo River Augmentation Demonstration Program
• Prepared For: USBR, Divison of Atmospheric Research
• Prepared By: Thompson, Wilderson, Griffith
• Date: 12/1/1987
• State: AZ
• Weather Modification - Doc Type: Scientific Study

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the SLW usually decreased rapidly to light or nil. The exceptions
were more frequent values ln the moderate to sometimes strong
range in the episodes where significant convection was present
or the general lack of SLW in the episodes which had predominantly
ice clouds (SS-10, the afternoon and evening of February 25
with ss-3 and the latter stages of SS-9). strong hourly averages
were observed for at least two hours or more in seven of the
episodes and two other episodes each recorded strong values
for one hour. During all the episodes, strong hourly readings
of SLW were recorded in 31 hours (8 percent of the total)
while moderate and s~rong values were observed (on the average)
in 32 percent of the hours with the median value between 27
and 28 percent.

Precipitation at Happy Jack averaged 16 hours per episode
but the median was much less (between 9 and 17 hours) suggesting
that a few episodes which had many hours of precipitation
probably biased the average. Happy Jack recorded 55 hours
of precipitation during SS-3 but there were four episodes
with no precipitation recorded at the site and several other
episodes had less than 10 hours of precipitation recorded.
Ina similar manner, Happy Jack precipitation total averaged
.54 inches (13.7 mm) per episode, including 3.07 inches (78
mm) during SS-3, but the median was much lower, between .12
and .19 inches (3-4.8 mm) per episode. On the average, for
each episode, precipitation at Happy Jack was recorded during
38 percent of the hours (median between 37-41 percent). Precipi-
tation was observed during 81 percent of the hours of SS-l
and 78 percent of the hours during SS-2. In fact, during
the Medina type A-1 storms, which included SS-l and SS-2,
precipitation was observed in 65 percent of the hours while

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