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<br /> <br />00234a <br /> <br />. <br /> <br />. <br /> <br />can be significantly increased during periods of severe drought during <br /> <br /> <br />specific growing seasons. Comments usually suggest some probability of <br /> <br />success for moderate droughts and little chance of success during extreme <br />droughts. Large percentage increases during dry periods may.be meaning- <br />less since the volume increases may be very small. The problem of severe <br /> <br />short term droughts while critical in the Great Plains, is not as important <br /> <br /> <br />in the Pacific Southwest. In the Southwest, the greatest need for con- <br /> <br /> <br />vective rainfall is in the spring and early summer, when the chances of <br /> <br /> <br />rains that can be seeded are the least likely. For example, when clouds <br /> <br />are rare or nonexistant, then weather modification based upon seeding <br /> <br />individual clouds cannot be expected to increase rainfall. Weather <br /> <br /> <br />modification under these conditions cannot alleviate the seasonal droughts <br /> <br /> <br />in the Southwest. <br /> <br />Other <br /> <br />Scientists are divided on the possible modification of violent <br /> <br />convective storms that produce squall lines, hail, and intense rainfall. <br /> <br />Future technology in weather modification of violent storms is also <br /> <br />uncertain. However, such storms are of considerably less significance in <br /> <br />the Pacific Southwest than in the Great Plains. <br /> <br />The Forest Service has experimented on lightning suppression in <br /> <br />Montana and Wyoming with considerable success. However, several inves- <br /> <br />tigators in Arizona and New Mexico have pointed out the high correlation <br /> <br /> <br />between lightning and rainfall, so lightning suppression in the Southwest <br /> <br /> <br />might also mean decreasing rainfall. <br /> <br />COMMENTS <br /> <br />The following comment on the present state-of-the-art appears in <br /> <br />6 <br />