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Last modified
7/28/2009 2:28:58 PM
Creation date
10/1/2006 2:17:17 PM
Metadata
Fields
Template:
Weather Modification
Applicant
Western Kansas Groundwater Management
Project Name
Western Kansas Weather Modification Program
Date
1/1/1999
Weather Modification - Doc Type
Report
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<br />Two, or more, colliding gust fronts frequently create extremely severe storms, although <br />the severe storms are often short-lived. Severe aircraft turbulence is frequently found in gust front <br />air between the parent storm and the leading edge of the gust front. Ahead of the gust front the air <br />is generally smooth. When gust fronts drop out of high-based clouds, micro-burst activity occurs <br />which has been known to flatten buildings, crops and cause aircraft accidents during landing and <br />take-off. <br /> <br />Gust fronts emanating from Convective Scale interaction, as described above, frequently <br />occurs on the WKWMP; when identified and reported by pilots, or seen on radar, its occurrence <br />and direction of movement is monitored carefully for any subsequent storm growth developing <br />above it. Also, it has been observed that severe new storm growth often develops in weak, old <br />non-hail bearing precipitation areas, which are undercut by gust fronts. Satellite imagery can also <br />give advance warning about subsequent new storm development potential which can't be seen <br />immediately on radar or visually by pilots. <br /> <br />Under some conditions rainfall augmentation over large areas have been produced by <br />seeding atop the leading edge of a gust front as air is lifted over it which causes only weak: <br />cumuliform clouds to form. Updrafts found above gust fronts have wide variability---from 100- <br />200 feet per minute to a more normal 1,000 - 2,000 feet per minute, or more. If this particular <br />condition occurs at night with little threat of hail developing from new storm growth and weak <br />updrafts are prevalent, rainfall stimulation seeding can be highly productive over large areas using <br />wing generators. It's likely under these conditions the dynamic effect is markedly changed, <br />whereas, the static seeding effect is being achieved. In such cases the cloud's microphysical <br />characteristics are being altered by seeding. It is likely that hygroscopic seeding above a gust front <br />may also produce good results, however, it has not been tested on this program yet under the <br />circumstances given. <br /> <br />There is another form of cloud system which has important seeding potential, on occasion, <br />for producing precipitation in Kansas: the multiple-celled-convective system. This starts as a <br />cluster of small, weak air-mass clouds developing within a relatively small area---typically 10 - 30 <br />miles in diameter. If one, or more, clouds can grow sufficiently to merge with another, the <br />resulting merged cloud tends to continue growing, thereby promoting further cloud mergers <br />which further increases both cloud volume and intensity. Such cloud systems are capable of <br />eventually producing precipitation over large areas and persisting much longer than they normally <br />would, otherwise. Updrafts initially found within such a cluster of cells are often embedded and <br />difficult to locate, however, once such a system grows to a certain size, updrafts generally <br />organize better and the cloud system 'becomes easier to continue seeding. Under natural <br />conditions, many times these are regions become the "first echo" development seen on radar. First <br />echoes have a high correlation to being the day's first severe storm. <br /> <br />Most of the important research on the dynamics of the multiple-celled-convective system <br />was done in the 1980s in West-Central Texas. Radar studies of Northwest Kansas clouds from <br />1972 to 1974 found this area was fertile for such development and data comparisons suggest <br /> <br />11 <br />
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