WMOD00313

• Title: Cloud Physics Studies in Utah During 1978
• Date: 9/1/1978
• State: UT
• Weather Modification - Doc Type: Report

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SUMMARY - 27- Mar>eh Z978

This research mission over the Uinta Range was flown prior to develop-
ment of precipitating clouds. The winds were light from the southwest and
the atmosphere was dry and neutrally buoyant. A southwest flow is a down-
slope flow from the Wasatch Range to the Uinta Range and hence no signifi-
cant clouds were present over the Uinta Range.
The second flight over the Uinta Range during this storm occurred
during the early morning hours on 22 March with takeoff from Salt Lake City
at 0730 and departure from the Uinta area around 1000. The flight track
over the Uinta Range is shown in Figure 4.2.8. The sounding taken during
descent into My ton VOR between 0800 and 0820 is shown in Figure 4.2.9.
Convective instability was present above 720 mb with clouds bases at
725 mb at OoC (2.7 km). The winds were light and variable below cloud
base. The winds at cloud base were from the southwest at 3 to 4 m s-l
and increased to 10 to 12 m s-l at 4.5 km. A sounding taken at 0935 (Fig-
ure 4.2.10) on the downwind side (north) of the Uinta Range indicated that
the atmosphere was neutral, implying that convective overturning had indeed
occurred. The winds on the downwind side were significantly less than
they were on the upwind side with maximum winds being about 5 m s-l at 4 km.
Figure 4.2.11 contains the streamlines and e analysis at 4.6, 3.7,
e
2.8, and 2.0 km. At 4.6 km the winds were from the south southwest at 5
to 6 m s-l with e increasing as the air approached Kings Peak (KPK).
e
This indicates that the air was indeed ascending in the cloud observed.
At 3.7 km, the winds veered more to the westerly direction and blew from
the southwest. Some diffluence around KPK is indicated and the increase in
e over the Uinta Range again implies that the air was ascending. Hori-
e
zontal wind speeds were on the order of 5 m s-l. At 2.8 km the winds were
almost due south. This altitude is very near cloud base. At 2.0 km,
which is only a few hundred meters above the ground, the winds were light
and variable approaching the mountain. The winds were then diverted around
the mountain. These winds agreed with the hodograph winds discussed above.
Figure 4.2.12 contains a series of analog traces taken from 0943 to
0949 which from Figure 4.2.8 can be seen to have been during the time when
the King Air was crossing the center of the Uinta crest line on a south-
bound heading. e values varied from around 315 K over the center of the
e
crest to 313 K on the southern edge of the crest. The liquid water as

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