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The chosen portion of the overall pass plot in Figure 13that is highlight in yellow had both cloud <br />droplets and rain drops as can be seen in the left plots. Again, the SF gas-detector plot suggests the presence of <br />6 <br />the gas in this portion of the cloud pass, but this is a faulty interpretation that is due to the confounding effects <br />of the strong updraft that existed in this portion of the cloud. Were it not for the gas plot, however, one might <br />erroneously have ascribed these larger drops to the hygroscopic salt-powder seeding. Although it would have <br />been convenient to claim this entire pass as a huge seeding signature, it would not have been honest, because <br />the facts suggest otherwise. It is likely that only the shallower upshear portion of the cloud had been affected by <br />the seeding when the cloud pass was made. The obvious point here is that the documentation of the effect of <br />seeding on cloud microphysics is a very complicated business that requires precise navigation and the tagging <br />of the cloud volume containing the nucleant with a tracer gas. <br />Figure 13. As in Figure 12 but for the downshear portion of the cloud pass where the cloud was much taller and <br />the rain shaft was located. <br /> It is unfortunate that additional measurement passes could not be made into this vigorous cloud because <br />of safety considerations. Considering the enormous effort that was expended to obtain this case, it is clear that <br />the information content from it is not commensurate with the level of effort. <br />8.3Results of May 31, 2005 <br />Operational Overview <br />(All times are GMT) <br /> This was research flight #14 on May 31, 2005 from: 19:40 – 22:40; 3 hours. Detailed documentation of <br />the operations on this day is given in Appendix E. <br /> The most productive day of SPECTRA II was May 31, 2005 when two experimental units were <br />obtained. A strong upper level shortwave had entered northeast New Mexico by late morning on May 31, 2005. <br />A low was centered in southeast New Mexico and the tail end of a cold front extending from the northern <br />Central Plains states into the northern portion of the Texas Panhandle triggered severe thunderstorms in <br />38 <br />