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WES'J.'JDdf KANSAS WEATHER MODIFICATlON PROGRAM a-wail: hail..n@pld.coa .met: http: / jwww.pld.coa/useJ;'$jhailaan/aaster.hHl!cEIV[D WEEKLY NEWSLETTER 96-20 SEP 0 5 1996 FOR THE PERIOD AUGUST 24 - 30, 1996 Colorado Waler Conservation Board General Interest: The summer rainfall pattern has completely changed from what was experienced prior to Memorial Day wee~end some three months ago (May 25th-27th), This period was generally credited with being the start of our relatively long, wet summer. Shown below are some standard long-term and short-term moisture charts from May 11th, two weeks prior to Memorial Day, and the same charts about three months later as of huqust 17th. ' These charts were selected because it was the nearest date prior to Memorial Day which showed both the Drought Severity (long- term Palmer index) and the crop Moisture (short-term crop need vs. available water in 5 ft. soil profile). ~y early May, in nearly all of the Southwestern and western one-third of Kansas, short-term moisture was considered abnormally dry to excessively dry; long-term moisture was similar, showing moderate drought in the same area. But, by late August the short- term picture had Changed dramatically showing favorably moist and abnormally moist areas stretching northeast across southeastern New Mexico, the, panhandles, Western Kansas, Central and Eastern Nebraska and Southeast South Dakota. Long-term, a moist area covers most of Western Kansas, north to south, and is neutral elsewhere in Kansas where climatolQgically average moisture is found. Obviously, whatever drought we had three months ago has long since ended on both the short-term and long-term scales. If there are any areas which have received below normal rainfall this summer in Western Kansas, they are isolated cases. LoOking onooth sides of Western Kansas, we see long-term extreme drought conditions west of us in Colorado and less moisture to our east in Kansas. Short-term, the pattern is the same. It is tempting to believe that cloud seeding was instrumental in ending the 1995-96 drought, but it wasn't. Nor were we responsible for the previous drought.. .both were due purely to overwhelming natural causes. The moisture conditions demonstrated here were used to point out that: (1) extreme changes in precipitation can occur naturally in a relatively short time, (2) extreme changes in precipitation generally occur over large geographical areas and, (3) once extreme changes in precipitation occur, a trend can persist for long periods. Too often cloud seeders get caught up in a weather trend, being blamed for droughts as well as floods when they occur. The reality is that in these extreme conditions we cause neither. Our effects, though important, are relatively small compared to the larger area effect occurring natura11y.