WMOD00390

• Title: A Proposed Wintertime Weather Modification Research Program for Colorado
• Date: 1/1/1980
• State: CO
• Weather Modification - Doc Type: Report

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system's seedability are as follows:
(1) Cloud base moisture of 2.0 gm/kgm or greater in clouds
over the seeded area as indicated on an adiabatic
diagram.
(2) A cloud depth of 2,000 feet or greater over the seeded
area. Either observed or indicated on a adiabatic
diagram. The moisture as assessed on an adiabatic
diagram must be 85 percent relative humidity or greater
to be indexed as representative of a cloud region.
(3) A cloud base height of 1,000 feet or less above the
average height of the seeded mountain crest.
(4) A pre-trough 500 mb temperature of -120C to -260C or
a post-trough average cloud top (either observed
or indicated on an adiabatic diagram) temperature of -120C
to -260C.
(5) Barrier crest (usually 14,000 feet MSL) wind speeds of
10 to 30 knots for pre-trough cloud systems, or
wind speeds of 10 to 40 knots for post-trough cloud
systems.
(6) A targeting wind direction based on the average between
the 10,000 feet MSL and 14,000 feet MSL wind directions.
As long as at least one-third of the target area can be
seeded with five or more ground-based generators, condi-
tions would be considered favorable for a seeding event.
(7) Additional considerations on the mode of seeding would
be made when surface winds at seeding sites are calm or
when shallow atmospheric inversions are occurring.
Expanded statements on t:he determination of each of these
meteorological characteristics associated with a cloud system's
seedability are presented in Appendix A.
b. Determination of Seeding Rate
A method of consistantly calculating and applying a seeding
rate to seedable cloud systenls has to be established for this
program. This established and consistent method of calculating
seeding rates should allow more meaningful evaluations to be made
of the seeding effects on the! various weather systems treated with

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