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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continuous) precipitation at a given point, which may vary
in length from a few minutes to several hours or even days.
These precipitation periods are generally referred to as storms
and may be of the kind that produce heavy amounts of precipitation,
either within a short duration or over a prolonged time period,
or they may produce moderate or only very limited amounts.

Examination of the synoptic weather charts and the precipi-
tation records from the seven recording gauge sites revealed
that during the ~pproximately two month period from January
11 (when the first precipitation gauges were activated) until
March 18 (when the last gauges were deactivated) there were
11 storm periods where the average precipitation over the
gauge network exceeded 0.05 inch (1.27 rom). For this analysis,
to qualify as a storm, 0.05 inches was considered to be the
minimum precipitation total averaged over the gauge network.
The storm duration was determined by the beginning and ending
of the more or less continuous precipitation recorded at the
majority of the gauge sites, or if there were significant
precipitation breaks, the interval between breaks was less
than 24 hours. Thus, the minimum break in precipitation between
storms was 24 hours and in most cases this interval was consider-
ably longer.

These storms took place over 28 days of the 67 day period
(42 percent) with over half of the days (15) occurring in
February. Obviously, these 15 days represented over half
of the total number of days in the month. During the other
months, which were both partial months, storm precipitation
fell on seven days in January (33 percent of the January 11-31
period) and on six days in March (35 percent of the period
from March 1-17). Most of these storms were spread out over

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