WMOD00058

• Contract/Permit #: #98-1
• Applicant: Western Kansas Groundwater Management
• Project Name: Western Kansas Weather Modification Program
• Date: 4/28/2001
• Weather Modification - Doc Type: Report

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Most used among the techniques of cloud top seeding aircraft on many other programs is
the dropping of ejectable flares from a belly rack on the cloud top plane, This type of seeding is
not done on the WKWMP primarily because of the relatively high cost for flares. It is much more
expensive to seed with flares than with dry ice, despite the sublimation (evaporation) occurring
with dry ice while kept in storage between operational periods. However, using either dry ice or
ejectable flares, the seeding technique is essentially the same: an'aircraft penetrates a new-growth
cloud and delivers the seeding agent of choice into the updraft column.

Over the years, both cloud physics research and results from other programs, much like
our own, have been applied to the WKWMP whenever possible to ensure we maintain reasonable
state-of-the-art. We test and implement new things ourselves when it appears it will enhance our
overall operational capability and keep costs at reasonable levels,

The cloud systems listed below, and variations of them, are most responsible for
producing rain and hail in Western Kansas:

(I) the air-mass storm complex

(2) multiple-celled storms

(3) the squall line

Air-mass storms often become complex after starting out as an isolated cloud system
having a well-organized cloud base and new growth updraft area usually visible around its base.
Multiple cloud turrets often develop around the initial "parent" storm; subsequent storm
movements can become erratic depending upon several factors such as its severity, terrain effects,
dynamic factors within the storm, cloud height, variability of wind speed and direction with
height plus the blocking of steering winds caused by large upwind cloud systems,

Air-mass storm complexes often transition into large multi-celled systems, a line of
storms containing multiple cells showing characteristics similar more to those of a small squall
line. During the gradual development of these multi-cellular lines, cloud base updrafts frequently
shift around although they are still found near some of the individual cell elements comprising it
making proper seeding treatment quite difficult at times.

Fig. 2 shows a "classic" storm with new growth on its upwind (left) side. Updraft air
found upwind of a storm's direction of movement is termed "trailing" or "back side." Whereas,
the downwind, front side is its trailing side. Most often, updrafts pertinent to the hail process are
found along its trailing edge below cloud base at some distance behind the precipitation.

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