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<br /> <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br /> <br />28 <br /> <br /> <br />and 17, Note that most thunderstorm genesis occur between 1100-1500 MDT. <br /> <br />This suggests that there is a diurnal dependence on the sun to initi- <br /> <br />ate the primary destabilization which begins over the mountains early <br /> <br />in the day and proceeds eastward onto the plains, <br /> <br />The mean number of echoes which later grew into thunderstorms <br /> <br />observed to initiate over each grid square is seven. In Figure 18, <br />.. <br />the number in each grid square refers to the number of echoes observed <br /> <br />to initiate over that grid square compared to the mean number. Clearly <br /> <br />grid squares above 5000 feet in elevation generated many more thunder- <br /> <br />storms than those located at lower elevations on the plains. The most <br /> <br />important result af this figure is the existence of several grid <br /> <br />squares which produced 10 or more thunderstorm echoes above the mean, <br /> <br />The important grid squares are Bl, 2, 3, 5, 7 and 8; Cl, 7, 9, 12 and <br /> <br />IS; and 01, 7 and 9. These squares wiU be referred to as <br /> <br />hot spots in this study. Figure 19 compares the echo generation for <br /> <br />all grid squares above 5000 feet in elevation above the mean for all <br /> <br />squares of 11 echoes. The same squares appear again as the primary <br /> <br />" <br />,], <br /> <br />generators of thunderstorm echoes. The statistical significance of <br /> <br />these squares '''as tested using the Poisson distribution test for aU <br /> <br />i <br />i <br />, <br /> <br />r <br /> <br />grid squares above 5000 feet. The test showed that there was less <br /> <br />;i <br />i <br />~:! ,:1 <br />1:,,1 <br />F\ <br />IiI., <br />r-:\ <br />'1"i <br />12., ~ <br />'I <br />i, P , <br />'-I:' <br />j') <br /> <br />'I. j;" '.', <br />~ }:1:. _'I': <br />::1" t <br />! ~, <br />d ,,,. <br /> <br />than one chance in a million this echo production was a random <br /> <br />occurrence. The grid squares included in the test were all those with <br /> <br />at least SO percent of the square above 5CaO feet in elevation within, <br /> <br />125 nautical miles of the radar, <br /> <br />A compal'ison of the number of thunderstorm echoes generated by <br /> <br />grid squares of different elevations is presented in Table 4. TIlis <br /> <br /> <br />table compares both the absolute number of echoes initiated over grid <br /> <br />