Laserfiche WebLink
<br /> <br /> <br /> <br /> <br />27 <br /> <br />I <br />I <br />I <br /> <br />(LHX) , These late initiation times observed over the river valleys may <br /> <br />be related to the suppressive effect of the valley breeze circulation <br /> <br />of the Rocky Mountains discussed in Dirks (1969) and weaker valley <br /> <br />breezes formed by the ridges which jut out into the plains. This <br /> <br />would support the existence of Dirks' western cell of the hypothesized <br /> <br />circulation. No evidence was found of the second cell. <br /> <br />.. <br />Figure 15 depicts the time in MDT that the maximum number of <br /> <br />convective echoes which later grew into thunderstorms were found to <br /> <br />initiate over a grid square. Again the elevated topography exhibits an <br /> <br />earlier initiation time than the plains. A secondary maxima of echo <br /> <br />initiation is found during late afternoon or early evening in some <br /> <br />grid squares. It is most prevalent along the foothills from Fort <br /> <br />I, <br />',: <br /> <br />Collins (FCL) to Denver (DEN), near Colorado Springs (CaS) in the vicin- <br /> <br />~ : <br />; <br /> <br />ity of Pikes Peak, and on the sourthern faces of Cheyenne Ridge and <br /> <br />'I .' <br />-: J' <br />I <br />j <br /> <br />Palmer Lake Divide, These secondary maxima appear related to late <br /> <br />afternoon heating of the western slopes of the Front Range and possibly <br /> <br />the formation of a low level jet over the plains in the case of the <br /> <br />ridges. <br /> <br />It is interesting to note the apparent evening maxima of thunder- <br /> <br />r <br /> <br />storm generation in both the South Platte and Arkansas River Valleys. <br /> <br />This strongly suggests that factors other than thermal destabilization <br /> <br />i <br />I <br /> <br />are "forcing" this late convective development. It is possible that <br /> <br />this maxima may be related to a reversal in the mountain-valley breeze <br /> <br />"n,; <br />,i") <br />ii, <br />I' <br />~ I <br /> <br />circulation. Do.nslope drainage I"inds off the ridges may induce a <br /> <br />a, <br />'" <br /> <br />slight low level convergence field in the valleys. <br /> <br />l,i <br />1': <br />I; I <br />>' ,J': \ <br />'J,j <br />;j'i <br />I I <br />,ln <br /> <br />~ . <br /> <br />The relative and cumulative percent of echo generation over all <br /> <br />grid squares for each hour of the day is illustrated in Figures 16 <br /> <br />, <br />\1 ik <br /><i" j:, <br />~, <br />