WMOD00218

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

In the fOllowing sequence of figures both the short and long-
term moisture changes throughout the United States are shown. These
are the official figures from the NOAA/USDA Joint Agricultural
Weather Facility. The indices are produced at the NOAA/USDA Joint
Weather Facility in Washington, D.C. with the Short-Term Drought
Severity Index released weekly, whereas, the Long-Term Palmer Index
is relea~ed bi-weekly. These can be found as they become available
in the periodical, "Weekly Weather and Crop Bulletin."

The Palmer Long-Term Drought Severity Index shows USA soil
moisture conditions is shown for the period of time which nearly
parallels our WKWMP season and is not prone to short-term moisture
changes. The index. is developed from official measurements.made at
second-order weather observing sites, around 30 - 40 miles apart in
our area. Normally, this index takes periods of weeks or months to
change, not days. While not perfect, the categorized areas shown
generally tend to exhibit the real-world crop moisture pattern.
Figures 7, 9 and 11 show how the index changed between late April
and late September, 1997. The WKWMP target area on April 26th
appears fairly uniform, tending to be just slightly on the moist
side. However, by Sept. 27th the long-term index showed most of the
southern part of the WKWMP target area had become moist or slightly
above normal; whereas, the northern portion was more in the normal
range, to slightly above normal range. Most of Eastern Colorado,
north to south, lay in an area of severe drought. '

The Crop Moisture Index is a measure of the more rapid response
to rainfall over a shorter time period, or lack of it, almost from
week to week. Figures 8, 10 and 12 show the state of the short-term
moisture near the beginning of the 1997 WKWMP season, the mid-point
and the end.

,

Fig., 12 shows that as
for the WKWMP, in all but a
"Favorably Moist", nearly
pattern.

of Sept. 27th, the short-term moisture
small fraction of Northwest Kansas, was
parallel to the long-term moisture

Most of Eastern
"Abnormally Dry" and
pattern.

Colorado's short-term moisture is labeled
nearly replicates its long-term moisture

The Figs. 11 and 12, are the long-term and short-term indices
for the end of the season, but do not seem to accurately reflect
the pattern seen in Fig. 6. This is one of the values of having a
rainfall network which can be overlain on the "official" data to
obtain a better perspective of soil moisture conditions around the
region. Most likely, significant portions of the WKWMP target area
were well above the official NOAA/USDA figures shown. If anything,
the heavier moisture realized in some sections of the target area
will be beneficial to them, whereas, the WKWMP may have their work
cut out for them stimulating rainfall in much of the rest of the
area come next spring.

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