WMOD00313

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

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CHAPTER 4
STORM CASE STUDIES

4.1 Storm of 11-13 March 1978
The first storm studied in the Utah project occurred on lIt 12 and
13 March 1978. During this storm, a mission was flown In the early
afternoon of 12 March over the Uinta Ranget and a second flight was flown
late in the afternoon of 12 March along the Wasatch Range. Figure 4.1.1
contains surface maps and 500 mb maps for llt 12, and 13 March at 0500*.
At 500 mb on 11 March, Utah was beneath the center of a small ridge with
well-defined short waves to the east and west of Utah. By 12 March the
short wave along the west coast of the United States had intensified
significantly and was moving across Utah during the day. By 13 March
this short wave had moved on eastt leaving Utah in a northwesterly flow.
The minimum 500 mb temperatures over Utah during this storm were colder
than -250C. At the surfacet a low pressure Center was located west of
Utah in Nevada on the 11th. This low center consolidated and formed a
cold front by the morning of 12 March. During the day this low pressure
center moved directly across the Salt Lake City area. On the 13th the
surface low was located in eastern Kansas.
Figure 4.1.2 is a map of the central part of Utah over which the
research flights were flown. The Individual ground generators operated
during this storm are indicated. Most of the generators were turned on
during the early afternoon hours on 12 March, and were turned off late
in the morning on 13 March. From this Figure It may be seen that the
ground generators were operated for the Wasatch Range onlYt and that no
ground generators were operated in the vicinity of the Uinta Mountains.
There were about 2 1/2 hrs of aircraft seeding in the southern part of
the Wasatch Range on 12 March.
Figure 4.1.3 Indicates the number of ground generators operated at
various times on 12 and 13 March. From this Figure it may be seen that
by 1600 on the 12th there were 36 ground generators operating and that
the seeding aircraft operated from 1435 to 1715. After 0800 on 13 Marcht

*All times are Mountain Standard Time.