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<br />Significant progress was accomplished on the forecasting and definition <br />of the PET's (precipitation echo types). The continuing development and <br />use of the SCPP suspension criteria commanded a considE~rab1e portion of <br />time during the 1979-80 field season. A number of results are worthy of <br />comment: <br /> <br />1. Observations of warm storms that produce hec!lVY precipitation <br />continued to show a very efficient precipitation formation process. <br />Only small quantities of liquid water were found during several <br />events with high water volume and high rainfall rate. <br /> <br />2. The limited number of seeded events contributed to our knowledge <br />of the seedabi1ity of these storms. It was established that a very <br />effective way to disperse material was to release it into a strong, <br />vertically sheared wind field. Nonrandomized seeding experiments in <br />isolated postfronta1 cumulus clouds have shown similar effects from <br />s.eeding with dry ice and AgI flares. Preseeded values of liquid in <br />the two clouds were from 0.2 to 0.4 g/m3. Ice crystals were not <br />detected. Within 20 minutes after seeding one cloud with dry ice and <br />the other with AgI flares, only a small amount of liquid water <br />remained, and ice crystal concentrations were near 100/L. The few <br />randomized and nonrandomized experiments conducted during the 1979-80 <br />season seem to indicate that the lower release rates of dry ice and <br />the AgI flares are generally effective in postfronta'l cumulus clouds. <br />Higher release rates can be used in some conditions, especi ally in <br />ce 11 s. <br /> <br />1-10 <br /> <br />-' <br /> <br />e <br /> <br />e <br /> <br />e <br />