WMOD00574

• Title: Studies of Wintertime Storms Over the Tushar Mountains in Utah
• Date: 3/1/1986
• State: UT
• Country: United States
• Weather Modification - Doc Type: Report

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data averaged over approximately 20 minute periods: during scan mode,

one azimuth-averaged value was plotted for each complete scan, which

takes about 20 minutes; and during zenith mode, the data were averaged
for 20 minutes to be approximately consistent with the scan data. Two
cloud top temperatures are plotted during phase I because the radar
indicated two separate layers. The thick cirrus layer probably had high

ice concentrations and no liquid water because of its cold temperature,

and conversely, the low stratus cloud probably had low ice concentration

and contained the bulk of the liquid water detected by the radiometer.

Apparently the cirrus layer was not seeding the warm stratus below,

because the precipitation rates were small even though there was

considerable liquid water. As phase I ended, the cirrus cloud dissipated

and left altocumulus with tops slightly warmer than -20oe. This was

apparently not cold enough for significant precipitation to develop in

phase II. When the deep convection of phase III began, cloud tops rose

to -25oe, and with the abundant liquid water, precipitation was heavy.
In the final phase of the STORM, both liquid water and precipitation
dissipated.
The bottom panel in Figure 9 shows surface measurements of
supercooled liquid water which were obtained with a Rosemount icing
detector located near the crest of the Tushar Mountains (Solak and
Allen, 1985). During the first half of the STORM, the trend of this

liquid water measurement was consistent with the Merchant Valley

radiometer data. travel time from Merchant Valley to the ridge was about

20 minutes. However, during the later, heavy precipitation periods, the

low altitude liquid water was relatively less. This is consistent with

the expectation that the low altitude liquid water was strongly depleted

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