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<br />D R AFT <br /> <br />indicators or predictor variables that will indirectly measure or <br />predict the presence of the opportunity conditions for enhancing <br />precipitation from a cloud. The basic hypothesis from the prevlous <br />studies remains the same: when a cloud has abundant supercooled <br />water, the precipitation falling from it can be enhanced if seeded; <br />when it does not have abundant supercooled water, its precipitation <br />can be decreased if seeded. It is because more natural, as well as <br />artificial, ice nuclei are active at colder temperatures that warm <br />clouds tend to contain more liquid water than cold clouds. Therefore, <br />the traditional seeding "window" has been one that defines clouds <br />with some temperature range of warm cloud tops. This indirectly <br />indicates the likelihood of the presence of supercooled liquid water <br />in a cloud. But, it is not adequate in isolating the convective <br />portions of the storm which recent findings indicate might be very <br />important for treatment. <br /> <br />~ <br /> <br />Therefore, detailed studies of data from previous experiments need to <br />be continued to redefine, or at least refine, the traditional winter <br />orographic cloud "window" to criteria that lend themselves to recogni- <br />tion in something other than a post hoc analysis. This "window" could <br />be one defined by an index or by direct measurement of supercooled <br />liquid water. The seeding "window" or opportunity must have the <br />following attributes to be operationally viable: <br /> <br />~ <br /> <br />52 <br />