WMOD00454

• Title: Preliminary Analysis of the Hypotheses Used in the Utah Operational Weather Modification Program - Final Report
• Date: 11/1/1983
• Weather Modification - Doc Type: Report

23

slope of the regression line would be smaller. Because of the difficulty

of calibration and the unavailability of wirid tunnel calibration tests of

either of these two probes, quantitative assessment of the accuracy of

these instruments is impossible at this time. For completeness, both

values are reported in this document.

E. Case Study, Storm 9, Februa~ 1983
1. Synoptic Scale Environment

The surface and 500 mb analyses for 1200Z, 8 February 83 and OOOOZ,

9 February 83 are shown in Figures 4 and 5. At 1200Z, an occluded low

pressure system was located off the Oregon Coast with an occluded front

extending southward to a secondary low in west central Nevada. From this

low, a cold front extended south and west: through southern Nevada and into

southern California. A weak warm front also extended eastward from the

low just north of the study area. This weather system complex was

associated with a strong shortwave trough system moving eastward off the

coast. The 500 mb axis of this trough at 1200Z was just east of the

Nevada-California border.

During the 12 hours of significant precipitation occurring in the

study area, the secondary surface low pressure system moved rapidly

northeast into northern Wyoming, with the surface cold front crossing

Utah into Colorado. Microbarograph traces recorded at Beaver, Utah

indicated that frontal passage occurred at 2000Z. Aloft, the cold core

of the deepening 500 mb trough passed over the study area shortly afterward.

By 0800Z the axis of the trough was cente,red over the eastern Utah border.

2. Atmospheric Structure and Precipitation Echo Types (PETS)

During the 8 February 83 storm, four special rawinsondes were. launched

from the Adamsville site at l458Z, l752Z, 1948Z, and 0007Z (9 Feb). From