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<br />The storms form into four distinct CG storm cells by 1630 LDT (see Figure ]6): two as <br />multi-cells and two as single cell storms. Two of the cells are producing moderate rain <br />and one cell is producing heavy rainfall at this time with 43 CG's reported. Movement of <br />the CG storms continues to the north-northwest at 20 mph as the gust front propagates <br />slowly uphill into the plateau. <br /> <br />As the Opal stormes) enters its most intense phase with a rapid intensification of its <br />updraft, four distinct multi-cell storms can be identified. Seven cells within the four <br />storms are capable of heavy rain production at this time. The strongest storms are <br />becoming stationary along an east-west line by ]645 LDT (see Figure 17) and CG <br />production has nearly doubled to 71 strokes in ]5 minutes in an area extending from <br />3 miles east to ] 7 miles west of Nutria, Wyoming. <br /> <br />CG lightning production increases to 94 CG's from 1646 LDT to 1700 LDT as the Opal <br />storm complex continues to intensify (see Figure ]8). Five stOlID cells line up along a <br />roughly west to east line with the westernmost storrn over Nutria and the easternmost <br />storm 18 miles east of Nutria_ During the time interval of Figure 18 all storms have <br />become stationary. Due to merging processes, the storms become one complex of <br />multi-cell thunderstorms. Each of the five storms is producing very heavy rainfall. Most <br />of the heavy rain is falling east of US 30. No storm movement is noted during the next <br />15 minutes from 1700 LDT until 1715 LDT (Figure: 19). CG production drops to 58 <br />strokes as the storms merge into two large primary stonn centers. The clustering and <br />grouping of the CG's suggest that the most intense rain falls from 1630 LDll to 1715 <br />LDT. <br /> <br />Between 1715 LDT and 1730 LDT (Figure 20) the storm area shrinks but CG production <br />increases slightly to 61 strokes and shows little change from the previous 15 minutes. <br />The storm line moves about 3 miles north and maintains three primary cells of heavy rain <br />production within the one stonn complex. Rapid de,-intensification is noted from <br />1730 LDT until 1745 LDT (Figure 21). CG production drops to 15 strokes or to about 25 <br />percent of the previous 15 minutes strokes production suggesting that the storm updraft is <br />weakening. Perhaps the storm is choking on its own rain-cooled air. Storm aerial <br />coverage shrinks in size by almost 50 percent as the storm complex begins to break up <br />into smaller areas of moderate rain. These observations are directly supportive of the <br />rancher's comment that the storms ended by 1745 LDT. No heavy rain centers are <br />detected but three areas of moderate rain persist. <br /> <br />Surface and upper air analyses suggest that the surface trough and upper level thermal <br />short wave have crossed the Opal region and are beginning to move eastward. Local <br />wind fields associated with the gust front appear to be relaxing and the low level <br />convergence fields should have weakened considerably. It is easy to understand why the <br />storm weakens quickly after 1730 LDT. By 1800 LDT (Figure 22) only two small a.reas <br />of moderate rain remain and CG production has fallen to 19 strokes. In the next 15 <br />minutes the storm cells dissipate, lightning and rain production cease, and the Opal storm <br />is history. <br /> <br />40 <br />