WMOD00057

• Contract/Permit #: #90-3
• Applicant: Western Kansas Groundwater
• Project Name: Kansas Weather Modification
• Date: 9/13/1990
• Weather Modification - Doc Type: Report

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Often, two or more collapsing storms produce outflow
boundaries may eventually collide. When that happens, very severe
storms may be brought to life along these intersections and
cantinue repeating the process. Although severe turbulence 1s found
beneath the outflow boundaries, between the leading edge and the
precipitation af the parent storm, the air in front and above them
is usually smooth. Under some conditions, apparent excellent
widespread rainfall augmentation results have appeared after
"riding the gust front" and seeding the continuous updrafts created
along these boundaries.

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There 1s one other form of cloud system that appears to have
important seeding potential to produce precipitation in Kansas: the
multiple celled convective system. This starts as a cluster of
smalL, weak air-mass clouds, or storms, which develops over a
relatively small area---typically about 10 - 30 miles in diameter.
If one, or more, of the clouds grow sufficiently, it can merge with
others nearby and continue growing. The added growth allows the
merged storm to continue capturing other nearby sUlaller storms,
further increasing its size and strength. Such storms are
eventually capable of producing precipitation over large areas and
will persist longer than lIaverageH thunderstorms. Updrafts
initially found within the cluster of cells are often embedded or
difficult to locate, however, once the storm grows to sufficient
size, updrafts generally organize better. This type of storm system
has often responded positively to cloud seeding and can produce
abundant rainfall over 200 - 300 square miles, or more, at a time.

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Although almost all relatively recent research on the dynamics
of the multiple cell system has been done nearby in Texas, earlier
radar studies of Western Kansas clouds done by now-retired KSU
Professor L. Dean Bark, between 1972 - 1974, indicate Kansas is a
fertile area for the occurrence of these smaller clusters of cells-
--perhaps even better than Texas. As a result, over the past five
years these targets of opportunity have been eagerly anticipated.
Tims was, not too many years ago, little attention would have been
paid to these weak-appearing cloud clusters until they grew much
larger. However, aver the past few years we have found that when
we persist in ClUr seeding efforts at the early stages of these
systems development, we are often able to produce spectacular
results.

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