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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />the updraft locations. For pilots, the world of seeding becomes greatly chaflged when elevated <br />convection dominates the hail-producing process in severe storms, making seeding even more <br />hazardous. <br /> <br />This is what appears to happen most times: A storm collapses, often it is part of a line of <br />severe storms. A large gust front develops out of it, however, instead of the storm continuing to <br />collapse afld die, strong new feeder clouds continue growing attached to the collapsing parent <br />storm giving the severe storm continued life. Normally, feeder clouds obtain their moisture from <br />be1ow-cloud-base air prior to storm collapse, however, post-collapse new-growth feeder clouds <br />continue forming around the parent storm but don't exhibit below-cloud-base updrafts, yet these <br />feeders are still able to continue fueling the hail-producing process. Once hypothesized is that <br />this can only happen due to some mid-level moisture upon which to feed, the new growth clouds <br />will continue to grow only as long as there is moisture sufficient to fuel continued severe <br />convective storm development. When this moisture source is exhausted, storms no longer form. <br /> <br />Presently, it is unknown exactly what is the most important factor, or factors, determining <br />whether or not a parent storm will collapse, or whether, after a short period of re-organization, <br />the storm will resume status as a newly invigorated storm. Some of the factors determining <br />whether such a storm will persist or die appears to depend upon the storm's location relative to <br />other storms, whether or not it is in the multi-celled line, what is its direction of movement, how <br />much atmospheric instability exists, what amount of mid-level (above cloud base) moisture is <br />present, the direction, strength and organization of the winds both at mid-levels afld at cloud top- <br />--there are undoubtedly other factors as well unmentioned as well. <br /> <br />There may be times when elevated convection is unrelated to post-collapse severe storm <br />conditions such as near the end of a line of storms where strong upwind mid-level air is directly <br />impacting the cloud cluster or line of clouds. Often, the winds near, or above, cloud base are of <br />jet stream velocity helping to force convective clouds to grow quickly on the upwind side and <br />become attached to the last cloud turret, even before the is cloud collapse. Or, mid-level moist <br />air above a cool, stable and dry inversion may promote elevated convection rather than surface <br />based. <br /> <br />What makes the persistent storm (growing by elevated convection) difficult to treat is that <br />after it has collapsed, no sustained, steady updrafts are found. The updrafts that are found below <br />cloud base are embedded in heavy turbulence along with equally sharp downdrafts. In fact, it is a <br />cloud seeder's "cloud from hell" seeding experience ifhe wanders into that area. At the same <br />time, above cloud base, the quickly growing feeder cells eventually produce precipitation cores <br />containing hail large enough to damage crops and property. This type of storm can only be <br />seeded effectively above cloud base where pilots report a considerable increase in turbulence <br />inside the new-growth clouds formed by elevated convection---much greater than if penetrating <br />non-elevated clouds. Absent elevated convection, new growth cloud seeding is relatively <br />'benign' . <br /> <br />13 <br />