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Show (5) -24C, the cloud top temperature below which seeding effect becomes negative. Figure 220 represents an overlay, to be used with environmental temperaturehumidity soundings, on pseudo-adiabatic charts. The seedability limits were taken from Table 19, but without restricting cloud tops to 14, 000 ft. MSL. The first step in using the chart is to overlay it on a pseudo-adiabatic diagram containing a vertical sounding of existing temperature-humidity curves. Then select the mode of seeding to be employed as follows: (1) If any portion of the saturated air column (cloud layer) reaches below -24C, 00 NOT SEED. (2) If the saturated column intercepts the -15C isotherm within either the seedable or highly seedable from Mt. Harris region, SEED FROM MT. HARRIS, provided no inversion exists between 650 mb and Mt. Harris altitude. (3) If the saturated column intersects the -15C isotherm within the airborne seedable zone, SEED FROM AIRCRAFT OR OTHER MEANS OF AIRBORNE DISPERSAL, preferably at or above the altitude of the -15C isotherm. (4) If an inversion exists between Mt. Harris altitude and 650 mb, DO AIRBORNE SEEDING. (5) Also, if the wind direction target limits for ground-based seeding are exceeded, DO AIRBORNE SEEDING, regardless of temperature indications from the overlay. 328 |