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

17

Four phases of this STORM were distinguished, based on static

stability, precipitation intensity and the amount of liquid water:

;

Phase I.

February 8, 1330 - 2100 (MST)
stab~e, stratified with layered clouds
little precipitation and moderate amounts of
supercooled liquid w~ter

Phase II.

February 8, 2100 - 0400 Fepruary 9
convectively unstable with little precipitation
and slight liquid water

Phase III. February 9, 0400 - 1300
convectively unstable, heavy precipitation from deep
clouds accompanying cold frontal passage,
moderate liquid water

Phase IV.

February 9, 1300 - 2100
stable, light precipitation, dissipating stage

In the following sections of this report, the overall STORM

structure and chronology will be described first. Then a detailed

account will be given for each of the four phases.

;

B. Synoptic Summary

This STORM was an upper level short wave that moved across the

western states from the nortpwest. The SOO mb map is shown in Figure S

at the time the surface cold front passed the project site in Utah. It

shows a weak short wave (note 12 hour height changes of only about SOm),

propagating through a broad, flat long wave trough located over the

western United States. The short wave moved relatively slow, about 10

miles per hour at 40 degrees north latitude. Thermal advection at 500 mb

was weak until OOZ 9 February; in the next 12 hours, the temperature

dropped from -200C to -2SoC.

I:

The surface weather map in Figure 6 shows that there were several

frontal features during this time period. ~s is typical for this region

during winter'. the stationary co14 front along the eastern side of the