Study on a significant precipitation episode in the western United States / Ira S. Brenner

This synoptic study for the period 22 September to 3 October 1974 involves a case analysis of an unforeseen major precipitation episode. This was associated with the merging of an inactive upper tropospheric perturbation that moved east-northeastward out of the subtropics and an inactive extraƯ tropical low moving southeastward. Prior to the amalgamation of the two systems, only specks of high clouds were associated with each. Almost immediately with the merging of the two systems, rapid downward penetration of the upper-level extratropical system to middle levels took place, as evidenced on VHRR satellite imagery by·the development of rather organized middle cloudiness. Within 24 hours, a distinct vortex comprising alI cloud levels was evident on satellite photographs, and a well-developed low center became established in the upper troposphere near the 300-mb level. Twenty-four hours later, a major surface storm was in existence. The major impact of this storm was an abrupt end to the California dry season. Western Region technical memorandum ; No. 98 Includes bibliographical references (page 5-6). 1975 NWS (National Weather Service) WR (Western Region) Library Public Domain 1931