WMOD00475

• Title: The Characteristics and Evolution of Supercooled Water in Wintertime Storms Over the Sierra Nevada: A Summary of Radiometric Measurements taken During the Sierra Navada Cooperative Pilot Project
• Date: 7/1/1987
• Weather Modification - Doc Type: Report

the storm. The duration of supercooled water in this portion of the storm

varied from 24 to 45 h with amounts ranging from 0.05 to 1.10 mm and peaks to
1.30 mm in .embedded convection. SuperGooled water was also observed in the warm
front regTon (0.05 to. 0~60 mni) and 'in isolated convective cells near the end of

the storm"

Occluded storms in the northeast Pacific typically produced a cold front at

the project latitude. In these storms, the greatest supercooled water was
measured in the post-frontal period, immediately following the passage of the

cold front. Values from 0.05 to 0.60 mm were observed for 11 to 32 h. Lower

quantitie~; of supercooled water (0.,05 to 0.20 mm) were sometimes observed in the
pre-frontal period and during the passage of the cold front. Infrequent peaks

of supercooled water were also associated with isolated convection late in the
post-frontal period. These convective conditions sometimes persisted for o'ver

24 h.

Dissipating storms accounted for the remaining storms within the zonal storm

'category. Supercooled water was generally present in clouds throughout the

or

lifetime of the storm. The greatest values ranged from 0.05 to 0.60 mm and were
associated with the pre-frontal altostratus. Within the weak frontal band, and

in the post-frontal environment, measurements ranged from 0.10 to 0.40 mm. The
continual presence of supercooled 'Nater along with low amounts of precipitation

in these cloud systems suggested an inefficient precipitation process.

2) The presence of supercooled water in meridional storms was influenced mainly

by the trajectory of the storm. The meridional category comprised two storm
types: cutoff circulations near 400 N latitude and rapidly digging systems in
northerly flow.

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