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\ I I I I I I I I I I , I I I I I I I I I Most important to Western Kansas is the "cold" cloud. Cold clouds have a portion of their volume which have grown into a temperature range below freezing. It is the interaction between' supercooled water drops and ice crystals which initiates and promotes the process most responsible for producing significant precipitation in Western Kansas. The prevailing hypothesis under which the WKWM Program hail suppression portion operates is that hailstones grow to large sizes because there are too few ice crystals formed naturally in clouds during vigorous thunderstorm growth, thereby allowing relatively abundant supercooled clciud water to collect upon relatively few numbers of ice particles and other hail embryos. All too often those particles grow into hailstones too large to melt before reaching the earth's surface. Current theory is that by vastly increasing ice crystal concentration within these ice crystal-deficient clouds, we are strongly increasing the competition for available cloud water thereby preventing hailstones from growing to a size large enough to damage crops and property. Property type, crop type, stage of crop growth and hail size are all important factors in determining damage severity. Research has found that hail growth and movement within storms, especially very severe ones, can be very complex. However, most long-term hail suppression programs use similar seeding hypotheses and seed clouds in much the same way we do in Western Kansas. In 1994 the Kansas Water Office published the most recent evaluation of the WKWMP finding a 27% reduction of crop- hail damage statistically significant at the 5% level with a Benefit-to-Cost ratio of 37 : 1. The hail suppression seeding agents used on the WKWM Program are either silver iodide- based or dry ice and are delivered directly into growing clouds by aircraft. The silver iodide seeding agents are vaporized in the updrafts found at cloud base, whereas, dry ice is dropped directly into growing cloud updrafts at temperature levels of -1 OC, approximatelhy an altitude of around 20,000 feet in mid-summer. Hygroscopic flares, first tested in 1997 and used for a short time in 1998, appear to be useful in attempting to stimulate rainfall. These flares are composed of sodium iodide, potassium iodide and lithium chloride. Unlike the silver iodide-basded seeding agents, hygroscopic particles can enhance rainfall in both warm and cold cloud temperature environments. There are still some lingering questions about the viability of hygroscopic seeding agents for use in hail suppression. Over the years, the results from cloud physics research and other programs much like our own have been applied to the WKWM Program whenever possible. This helps ensure that the WKWMP retains in a reasonable state-of-the-art moc!e. We try to implement new ideas and test discoveries of new technological developments whenever possible, if it can be adapted to our specific conditions within our limited budget. Our innovations, however, generally have tended to be more in the area of enhancing our operational capability. High numbers of ice nuclei can be produced from our liquid, silver iodide-based, seeding agent in a wing-tip generator by first vaporizing the solution. Wing generators are mounted to the tips of cloud base seeding planes and employ a combustion process in which a 2% silver iodide liquid seeding solution produces trillions of ice nuclei per gram of silver iodide consumed. The wing generators 5