Laserfiche WebLink
<br />12 <br /> <br />1 <br />Mexico at 1700 MST, January 15, 1970. As the trough passed over the <br /> <br />experiment site the wind shifted to northwest and provided the flow <br /> <br />pattern appropriate for the experiment. Quite weak surface pressure <br /> <br />gradients were in existence over the experimental site (see Figure 3). <br /> <br />With time, however, the low east of the area in the Texas panhandle, <br /> <br />associated with the upper trough deepened and the upper trough developed <br /> <br />into a cut-off system and slowed down considerably. <br /> <br />Locally the character of the orographic storm appeared to change <br /> <br />over the period of study. Precipitation started by 1200 when the lower <br /> <br />winds had shifted from about 2700 at 0900 to 3000. The upper winds <br /> <br />were still westerly but becoming more northerly. All winds continued <br /> <br />to shift to the north until they reached 3300 at around 1400. Light <br /> <br />snow fell until shortly after 1800 when the snow stopped. After a <br /> <br />short period of no snow, highly variable snow resumed by 2000 and con- <br /> <br />tinued to fall until roughly 2300. A layer of warm air near 600 mb. <br /> <br />had reached Camp Hale by 2000 (Figure 4) reducing the stability of the <br /> <br />air up to about 525 mb. The snow during this latter period was spotty <br /> <br />and typical of convective activity. Also, at 2300 the winds started to <br /> <br />shift back to a more westerly direction. By 0000 on the 16th, the <br /> <br />winds were back to 3000, The precipitation episode seemed to have three <br /> <br />phases: First a period of snow from a stable orographic cloud, then a <br /> <br />period of transition with no snow and then a system in which convection <br /> <br />dominated over the stable cloud. <br /> <br />lReference to time in this paper will mean local time (Mountain <br />Standard Time). <br />