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 total precipitation with the average precipitation per
gauge per episode nearly 0.10 inches.

Exclusive of the short term episodes (6 hours or less
duration), the longer episodes (of which there were 65) averaged
16.4 hours in duration, with a median of 12 hours. The longest
episode lasted 50 hours and, by definition, the shortest were
seven hours in length. All of these longer duration episodes
occurred during a synoptic scale event. These 65 episodes
represented only 30 percent of the total but they accounted
for 89 percent of all of the precipitation within 73 percent
of the precipitation hours. Average precipitation per gauge
per episode during the longer episodes was 0.71 inches. As
might be expected, only 11 percent of these episodes had precip-
itation totals of less than 0.10 inch, with the least being
0.022 inches (during an 8 hour period). The episodes of longer
duration may offer the greatest opportunity for significant
precipitation enhancement, provided they meet seedability
criteria.

For all 217 episodes, the average duration was 6.7 hours
but the median was only 3 hours. Average precipitation per
gauge per episode was 0.25 inches but the median was only
0.06 inches.

3.2.8

Longer Duration Episodes

The data from Figure 3.4 and Table 3-6 indicates that
a large number (39 percent) of the episodes are of very short
duration (2 hours or less), and generally contribute little
to the storm precipitation totals. The data suggest many
of these episodes could be the result of light showers or

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