WMOD00310 ‎(2)‎

• Project Name: Sierra Cooperative Pilot Project
• Title: The Characteristics of Evolution of Supercooled Water in Wintertime Storms Over the Sierra Nevada
• Date: 9/9/1988
• Weather Modification - Doc Type: Report

1007

SEPTEMBER 1988

MARK F. HEGGLI AND ROBERT M. RAUBER

-50

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FIG. 14. As in Fig. 5, but for 1200 UTC 7 January 1985 to 0600 UTC 8 January 1985.

00
(1/8)

21 18
TIME (UTC)

12
(1/7)

Sheridan at 0300 as the winds became calm. Soon after,
winds were weak and out of the north, marking the
end of the storm.
Discussion. The 6-8 January 1985 storm was one
of seven storms associated with a cutoff low or large
amplitude short wave at 400N latitude. Large ampli-
tude short-wave cases were combined with the cutoff
storms because the observed wind shifts were very sim-
ilar. Five of the seven storms were cutoff lows, and all
had complete radiometer datasets. Two of the seven
storms were associated with large amplitude short
waves, but neither had radiometer data available due
to rain at Kingvale. The evolution of supercooled water

15

in large amplitude short waves will therefore not be
discussed due to the unavailability of radiometer data.
The storm of 6-8 January clearly depicts the super-
cooled water transitions in cutoff storms. Three distinct
areas with different supercooled water characteristics
were observed: the prefrontal zone, the postfrontal/
pretrough region, and the posttrough area. Supercooled
water was often present within the prefrontal region.
Values of supercooled water up to 0.60 mm were found
in the: prefrontal orographic cloud, with embedded
convection producing peaks in excess of 0.70 mm.
Precipitation was generally less than 1 mm h -1. The
duration of prefrontal supercooled water varied from