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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by diffusional and accretional growth of precipitation particles falling
through the cloud.
The history of horizontal winds is shown in Figures lOa and lOb for
the Merchant Valley location. This figure was derived from Doppler

velocity data from the NOAA Ka-band radar; they used the VAD analysis

technique with 70 degree elevation angle. Minimum detectable radar

reflectivity was about -30 dBz. Doppler data are not available below

this reflectivity threshold. The figures show that the winds were

relatively constant over the Merchant Valley site throughout the STORM.

The similar history derived from the Adamsville rawinsondes is different

in two respects. First, the cold frontal passage was prominent at 0600

MST February 9 at Adamsville; it had the classical wind shift from

southerly to northerly components. But the front was virtually

unidentifiable in the winds over Merchant Valley. We surmise that the

cold airmass was not deep enough and did not have enough momentum to

reach the Merchant Valley altitude (800 m higher than Beaver). Second,

low level wind speeds from the two sites are not in agreement relative

to height above sea level, although they do agree relative to height

above ground. Apparently the valley and mountain had similar boundary

layer depths of about 1 km. The shear in the boundary layer was

moderate, 0.01 per second. The C-band radar, which was located in the

Beaver Valley, should provide more detailed information on these

differences. Because of the consistency in the winds over the Merchant

Valley location it is possible to cite 'typical' values for the altitude

range where most of the precipitation formed: 3, 4 and 5 km (MSL) as

2300 6m/s, 2460 18m/s, and 2600 20m/s, respectively.

Figure 11 is a repeat of Figure 4 with the data points for STORM 9

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