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<br />Air from below cloud base enters the air-mass storm from many direct- <br /> <br />ions. .The important updrafts to that volume of cloud where precipitation <br /> <br />particles are born and grow is normally found below cloud base at some dis- <br /> <br />" <br /> <br />tanc~ behind the precipitation area, usually along the trailing edge of the <br /> <br />.' <br /> <br />s"torm. <br /> <br />~, " <br /> <br />Well orgainzed air-mass systems often develop multiple shifting up- <br /> <br />draft areas when new surges of cumulus growth appear along its flanks or <br /> <br />when growing nearby as separate entities that later merge with the parent <br /> <br />storm. Air-mass storms sometimes eventually organize into lines which ex- <br /> <br />hibit some squall line characteristics. The location of the important <br /> <br />updrafts on these types of cloud systems are found in the frontal portion <br /> <br />along a line which can be a few miles to many miles in length. <br /> <br />The second kind of cloud system, the squall line, appears as an organ- <br /> <br />ized line of cumulonimbus clouds with the important updraft area found along <br /> <br />the leading, or frontal edge of the line of storms. ,Vmrtical updraft veloc- <br /> <br />ities often exceed 2000 feet per mintue. Roll clouds and updraft "scud" <br /> <br />clouds are often visible almost to ground level. Severe turbulence is <br /> <br />often assoicated with this inflow area although it tends to decrease rapidly <br /> <br />further from the precipitation core. Significant updrafts are seldom found <br /> <br />, , <br /> <br />:along the trailing edges of squall lines. <br /> <br />Earlier it was mentioned that dry ice and silver iodide remain the <br /> <br />,primary materials used in treating clouds. The WKWM program uses both ,and <br /> <br />delivers the seeding materials to the clouds by aircraft. <br /> <br />. <br /> <br />The seeding agent, silver iodide, is produced through a combustion <br /> <br />proe.,ss that forms literally billions of ice nuclei per gram of silver <br /> <br />iodide consumed. Acetone-silver iodide generators are placed in the position <br /> <br />of wing-tip.tankS on each cloud base seeding aircraft. Utilizing air from <br /> <br />a pressurized tank, an acetone-silver iodide liquid solution if forced <br /> <br />through a nozzle into a combustion chamber where the solution is ignited <br /> <br />-7- <br />