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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19-20) to about five (5.2) during storm number 10 (March 7-9).
Of the 11 storm periods, four had an average of about two
episodes per storm while three other storms had episode averages
near four.

3.2.11

Time Interval Between BPisodes

To observe how these episodes are likely to be distributed
within a storm period, the time interval between episodes
was examined. There was a great deal of variation but, for
those storm periods which contained two or more episodes,
the average time between episodes was 5.2 hours with a median
of 4 hours. However, the most frequent interval between episodes
was 2 hours (the minimum time to define the separation from
one episode to another) which occurred in 45 of the 141 episodes
(32 percent). At the other end, several of the intervals
between episodes were greater than 15 hours (four were 18
hours, one was 19 hours and one was 21 hours) which raised
the average interval time. A breakdown of the shorter duration
episodes (6 hours or less), which were 69 percent of the sample,
versus the longer duration episodes did not reveal any distinct
differences in regard to the average time interval between
episodes. The time between episodes averaged near 5 hours
for both categories ( the same as for the entire sample of
141 episodes). However, the median for the time interval
between the shorter duration episodes was 3 hours which was
2 hours less than the average and 1 hour less than the median
for the longer duration episodes. This might indicate that
there is some tendency for the shorter duration episodes to
occur closer together, and that the longer episodes represent
more organized precipitation periods within the synoptic scale

3-52