WMOD00412

• Title: Final Report on Utah Cloud Seeding Experimentation Using Propane During the 2003/04 Winter
• Date: 3/1/2005
• State: UT
• Weather Modification - Doc Type: Report

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Recommendations are given for further development of the promising technology of propane seeding of
winter orographic clouds. A longer-term randomized program of at least three winters duration is
recommended with a minimum of three dispensers located about 3 km crosswind of one another. This
would provide for routine seeding plume coverage of the central portion of the target area over the full
range of wind directions capable of producing SL W cloud. That approach and a more extensive
precipitation gauge network would permit documentation of the downwind extent of seeding
effectiveness and its magnitude, as well as a confirmatory test of the statistical suggestions resulting from
the current work. The authors are fully aware that a confirmatory experiment for winter orographic cloud
seeding has not been funded for decades, and that foreseeable research prospects appear little better. Yet
such testing, with supporting physical documentation, will eventually be required to put this promising
type of weather modification on a firm scientific basis. In the meantime, water users interested in using
cloud seeding to increase the winter mountain snowpack will continue to make choices with the best
available evidence. The 2003/04 Utah randomized experiment has provided important new evidence that
propane seeding is an option which should not be ignored, especially where mildly supercooled liquid
water cloud predominates.

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