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<br />THE FLOOD OF 1993 <br /> <br />Figure 1.3 Average and Observed Monthly Precipitation Totals for the Upper Mississippi River Basin. <br /> <br />8 <br /> <br /> I- <br />- - - <br /> - - J 11 - <br /> <br />7 <br /> <br />6 <br /> <br />~ <br />.. <br />.. <br />-a5 <br />c <br />.::::. <br />c <br />E<4 <br />- <br />" <br />- <br />'i5.. <br />03 <br />.. <br />.... <br />0.. <br /> <br />2 <br /> <br />o <br /> <br />7/92 9/92 11/92 1/93 3/93 5/93 7/93 <br />8/92 10/92 12/92 2/93 <4/93 6/93 8/93 <br />Month <br />I_A- c::::J1l1n ,oe! I <br /> <br />. <br />, <br /> <br />Source: u.s. Department of Commerce, NOAA, National Weather Service.6 <br /> <br />Rainfall amounts over the upper Mississippi River Basin <br />during the May-August 1993 period are umnatched in <br />the historical records of the central United States, In <br />July bmad areas in the lower Missouri River Basin <br />experienced rainfall amounting to four times normal, <br />The series of storms producing these record rainfalls <br />were remarkable not only in their magnitude but also <br />for their broad regional extent; record wetness existed <br />over 26,000 sq. mL of the upper Mississippi River <br />Basin. Seasonal rainfall records were shattered in all <br />nine states impacted by the deluge of 1993, Summer <br />rainfall amounts equalled those computed for storm <br />freqnencies having 75-year to 300-year recurrence <br />intervals. Figure 1. 4 shows the weather pattern that <br />existed in 1993. <br /> <br />these rains were associated wi th a typical summertime <br />pattern and not a return to the anomalous and persistent <br />June and July atmospheric conditions. <br /> <br />During the June-August 1993 period. rainfall totals <br />surpassed 12 inches across the eastern Dakotas, <br />southern Minnesota, eastern Nebraska, and most of <br />Wisconsin. Kansas, Iowa. Missouri. Illinois, and <br />Indiana. Over 24 inches of rain fell on central and <br />northeastern Kansas, northern and central Missouri, <br />most of Iowa, southern Minnesota, and southeastern <br />Nebraska. Up to 38.4 inches fell in east-central Iowa. <br />Generally precipitation amounts were 200 to 350 <br />percent of normal from the northern plains <br />southeastward into the central Corn Belt <br /> <br />I <br /> <br />10 <br /> <br /> <br />-~. <br /> <br />)' <br /> <br />.~ <br />". <br />it <br />.' <br />