WMOD00218

• Contract/Permit #: #97-3
• Applicant: Western Kansas Groundwater
• Project Name: Kansas Weather Modification
• Date: 1/1/1997
• Weather Modification - Doc Type: Report

VI. RAINFALL DISTRIBUTION

The season began much like the previous year: When the program
began April 23rd, the region was coming out of a very dry fall and
winter. Similarly, sub-freezing temperatures hit the area behind a
cold front (passing May 1st) and crop damage was damaged by frost
most in Northwest Kansas with lesser damage occurring in Western and
Southwestern Kansas.

After the WKWMP started, there were more severe storms and
clouds capable of producing hail occurring as'well as some which
were seeded to increase rainfall.. However, near Memorial Day in late
May, more generally widespread storms prevailed. Thereafter,
thunderstorms and rainfall were seen more frequently, especially by
mid-June when afternoon surface temperatures soared well into the
90s providing heat, to assist in afternoon convection.

In early July a low pressure system drifted east across
Southwestern Kansas providing instability and conditions favorable
to breed widespread numbers of thunderstorms. It was as if this
event was to be the climax to a rather moist 6-7 week period ending
in early July. NOTE: July 5th was the day with the most crop-hail
damage claims submitted from severe storm hail damage for the total
WKWMP. Upper ridging (high pressure) dominated the region for the
next 3 weeks and was not conducive to general, widespread rainfall.

Then, in early August, came the once-in-a-generation kind of
rainfall event---on the 6th and 7th. A cold, upper closed low
pressure system moved southeasterly from Idaho into Western Kansas,
while simultaneously a "back door" cold front had moved through
Kansas from east to west: Behind the cold front moist air was being
supplied to the low pressure system while also being forced to move
upslope, aiding in the production of clouds. Much of the middle and
upper atmosphere also was moisture-laden from cloud debris produced
by Mexican monsoonal moisture which earlier had moved from the
Southwestern U.S. into our region. In essence, there was moisture
at all levels of the atmosphere present when the upper low sunk into
Western Kansas. It was as if the low pressure system tried wringing
out all the moisture in the atmosphere as it passed Western Kansas.
Rainfall totals in northern Kearny County were thought to be highest
with over 10 inches recorded; 4 - 6 inches weren't uncommon over
much of the region. Most places received the equivalent of about two
summer months of precipitation in two days. Within a couple of days
after the major rain event, the target area began drying out with
fewer thunderstorms forming. A relatively drier weather pattern once
again set in for most of the rest of August with a flurry of storm
activity occurring from the 5th through the 14th of September.
Fig.6 shows what was the rainfall distribution for the May-August
period. in one inch increments.

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