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<br />A cursory look at the big September 4 case did not show obvious effects, <br />. but did verify that the C- 97 was operated in a logical manner for the cloud <br />and storm development involved and that, if the seeding is effective. the <br />observed precipitation could have benefitted from the seeding. The main <br />storm system became self-propagating. If the seeding aids in this organi- <br />zational aspect of the storm through stimulating precipitation, the ultimate <br />effects of seeding can be very large but ~x. difficuit to verify. <br /> <br />/:~ <br /> <br />September 6 featured a cluster of towering cumulus just off the watershed- <br />Sand SW of Sayre. Both types of seeding were employed. The rain was very <br />localized, but rather strong for such dry conditions. <br /> <br />September 8 the clouds were ,veaker still but this time right over Lake <br />Altus. Rain did fall on the Lake and watershed. <br /> <br />On September 30 there was an attempt ~o seed in a storm area which turned <br />out to be stratiform. <br /> <br />The last seeding, October 1, was of an extremely shallow and local system <br />moving over the Lake Altus watershed. A few minor showers occurred, both <br />naturally and in the seeded regi on. <br /> <br />Several points have no quantitative significance but deserve mention as they <br />may help direct thoughts toward evaluations of subsequent programs. The <br />hygroscopic plume from the C-97 could sometimes be observed from the <br />ground as it moved up into a cloud base. Observers reported being able to <br />see a discontinuity along this line for some time afterward. In the C-97 <br />on various occasions we felt we saw precipitation extending in unnaturally <br />straight lines, as though it was r.elated to prior passes of the aircraft. On <br />August 23 there were some major precipitation cells observed in the seeded <br />location which had virtually no cirrus, although adjacent cells were prolific <br />cirrus producers. A goal for the hygroscopic seeding is eventually to be <br />able to extract mC?re water from such a storm while producing less cirrus <br />and yet still keeping it self-propagating. Hail fell from some cells of that <br />August 23 storm, but it is not known just which ones. There was virtually <br />no hail from the huge, heavily seeded September 4 storm. <br /> <br />On several occasions (Aug. 24, Sept. 6) the precipitation from small <br />seeded clouds descended very abruptly, with rapid disappearance of the <br />parent cloud with very strong downcurrents, and ,\i th some surrounding <br />transient secondary buildups. An unusally rapid flushout of water might <br /> <br />31 <br />