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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In order to show what the general moisture pattern was like during the growing season we
will present several of two types of national moisture maps produced by the NOAAlUSDA Joint
Weather Facility showing: (I) the short-term Crop Moisture index, and (2) the long-term Palmer
Drought Severity Index. Figs, 6-18, on pages 39 - 44, show the short and long-term changes in
these indices during the 2001 season. The short-term Crop Mois.ture index is released every week
while the long-term Drought Severity index is released every second week The periodical,
"Weekly Weather and Crop Bulletin" presents these maps as they become available; also, they are
archived on the Internet at the Joint Agricultural Weather Facility (JA WF) website and available
to the general public,

The Crop Moisture index is a measure of the more rapid response to rainfall over a short-
term period, almost from week to week The figures show the changes valid at the dates given
for it. Not all months periods are presented.

The Palmer long-term Drought Severity Index shows national soil moisture conditions
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 a perfect representation at all geographical
locations in small-size areas, what is shown generally tends replicate a near real-world crop
moisture pattern existing in the larger region.

As the crop-year began, both short-term and long-term crop moisture was near normal
around Western Kansas (Figs, 6,7), This continued through May (Figs, 8,9) when we had our best
rainfall month of the season, however, the short-term component began turning dry and just
entering into Northwest Kansas (Fig 9), By late June the long-term Palmer Index remained
almost unchanged while the short-term dryn~.!'s continued moving southeasterly from Northwest
Kansas and settling over much of our target area (Figs. 10, II). Storms had begun to appear more
often in July, but by late July the short term dry component was still appearing over much of
Western Kansas and had affected the long-term index by this time (Figs, 12, 13). Kansas was near-
normal by late July for long-term moisture, Sporadic moisture was seen in August leaving a NE-
SW oriented narrow tongue of moisture over the southwest, central and northeast portions of the
target area while being surrounded by dry conditions everywhere else (Fig. 15). Long-term
moisture had improved slightly in a small region in the central part of the target area, leaving the
rest of it relatively unchanged (Fig. 14), Going into the end of the season, we experienced more
storms this September than in any other September we had worked in; long-term moisture was
near-normal, but in reality it was moving in the direction of drier indications and short-term was
moistly favorable by this time (Figs. 16, 17), Since Sept. 20th, hardly any significant rainfall has
occurred over the larger region as storms haven't been too widespread in the month after program
termination, But, it can change quickly as it did last year in late October,

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