WMOD00096

• Contract/Permit #: #80-2
• Applicant: Western Weather Consultants
• Project Name: N. Central Mountains
• Date: 12/1/1979
• Weather Modification - Doc Type: License & Permits

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Attachment B

SEEDING CRITERIA

TIle selection oE suItable cloud systems for seeding operations will be based
on an evaluation of multiple meteorological and cloud physics parameters.
It is the understanding that the following criteria will be adhered to:

a. Cloud base water - Natural Precipitation. Cloud systems with a
a cloud base water content of 1.5 gms/kgm (North Sector) to
J.B Kms/kgm (South Sector) or greater will be considered as
potentially seedable. In this consideration a weather system
will be evaluated for seeding potential if it is determined
that at least natural precipitation is likely to occur.

b. Effective temperature Pre-trough or Pre-frontal. Cloud
systems with a 500 ME temperature of _270 C or warmer will
be considered as potentially seedable.

c. Effective temperature Post-trough or Post-frontal. Cloud
systems with cloud top temperatures of -270 C (North Sector)
to -300 C (South Sector) will be considered as potentially
seedable.

d. Barrier level winds. Wind speeds from favorable directions at
heights approximately 2,000 feet above the seeded barrier of
30 knots or less for pre-trough cloud types and up to ~O knots
or less for post-trough clouds will be considered as potentially
favorable for seeding treatment. Some adjustments are made to
the acceptable wind velocity ranges depending on the width of
the barrier to be seeded.

e. Cloud base height. Cloud systems with bases less than 2,000
feet above the mean barrier height will be considered as
potentially seedable.

f. Additional weather system considerations. Additional adjustments
will be made on the seeding rate or the seeding potential of a
cloud system based upon the depth of the cloud syslem to be
seeded, whether the cloud system is indicating reLevelopment or
is near its decaying stage and whether the cloud/system has a
potential source of abundant natural nuclei from higher cloud
systems.

Once a weather system is considered seedable by evaluating the
above cloud and meteorological parameters, an appropriate seed
rate is calculated for the initial portion of the weather system.
As the forecast and observed parameters of the weather system
change seeding rates are re-evaluated and changed as is necessary
(or the new or expected cloud conditions.