The Role of the Elsinore Convergence Zone on Severe Weather Vulnerability in Southern California's Inland Empire

The Elsinore Convergence Zone (ECZ) is a vaguely studied weather pattern that is often a factor in forecasting maximum temperature, prevailing winds, and severe weather in the area of Southern California known as the Inland Empire. Surrounded by the Santa Ana, San Gabriel, San Bernardino, and San Jacinto Mountain Ranges, the valley floor ranges from 1,000 – 2,000 feet mean sea level (MSL) in elevation.

The ECZ is formed at a geographical meeting point of westerly and northwesterly onshore winds from the Los Angeles basin and southerly sea breezes from the San Diego County coastal plain. The winds eventually converge, frequently along a line from near Lake Elsinore, California to near Perris, California. The most significant impacts occur when summer monsoon thunderstorms are able to drift into the Inland Empire from the east. Storms anchor on the convergence zone, at times reaching severe limits and producing damaging winds, frequent lightning, large hail, and flash floods. However, the ECZ boundary may also increase low-level rotation and instability during winter season cold-core storms in the Inland Empire, causing an elevated risk of severe weather compared to neighboring population centers along the immediate California coast.

Analyzing case studies on days when unusually strong severe weather events were observed and linked to the ECZ, this research project explores and explains the scientific characteristics of the Elsinore Convergence Zone, its origins, and indicators for heightened severe weather vulnerability in the Inland Empire. The goal of this research project is to improve the accuracy of short-term (0-12 hour) forecasts for ECZ enhanced severe weather, which will ultimately improve awareness and understanding of severe weather development and intensity in Southern California.