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<br />ATTACHMENT B <br /> <br />SEEDING CRITERIA <br />Established October 28, 1981 <br /> <br />The selection of suitable cloud systems for seeding operations will be based <br />on an evaluation of multiple meteorological and cloud physics parameters. It <br />is the understanding that the following criteria will be adhered to: <br /> <br />a. Cloud base water - Natural Precipitation. Cloud systems with a <br />cloud base water content of 1.5 gms/kgm (North Sector) to 1.8 <br />gms/kgm (South Sector) or greater will be considered as potentially <br />seedable. In this consideration a weather system will be evaluated <br />for seeding potential if it is determined that at least natural <br />precipitation is likely to occur. <br /> <br />b. Effective temperature Pre-trough or Pre-frontal. Cloud systems <br />with cloud top temperatures of -27 degrees C or warmer will be <br />considered as potentially seedable. <br /> <br />c. Effective temperature Post-trough or Post-frontal. Cloud systems <br />with cloud top temperatures of -27 degrees C {North Sector) to -30 <br />degrees (South Sector) will be considered as potentially seedable. <br /> <br />d. Barrier level winds. Wind speeds from favorable directions at <br />heights approximately 2,000 feet above the seeded barrier of 30 <br />knots or less for pre-trough cloud types and up to 40 knots or less <br />for post-trough clouds will be considered as potentially favorable <br />for seeding treatment. Some adjustments are made to he acceptable <br />wind velocity ranges depending on the width of the barrier to be <br />seeded. <br /> <br />e. Cloud base height. Cloud systems with bases less than 2,000 feet <br />above the mean barrier height will be considered as potentially <br />seedable. <br /> <br />f. Additional weather system considerations. Additional adjustments <br />will be made on the seeding rate or the seeding potential of a <br />cloud system based upon the depth of the cloud system to be seeded, <br />whether the cloud system is indicating redevelopment or is near its <br />decaying stage and whether the cloud system has a potential source <br />of abundant natural nuclei from higher cloud systems. <br /> <br />Once a weather system is considered seedable by evaluating the <br />above cloud and meteorological parameters, an appropriate seed rate <br />is calculated for the initial portion of the weather system. As <br />the forecast and observed parameters of the weather system change, <br />seeding rates are re-evaluated and changed as is necessary for the <br />new or expected cloud conditions. <br />