Differentiating Between Warned and Unwarned Tornadoes in California

On average, over 1,000 tornadoes strike the United States annually. Many of these severe weather events occur without any warning from the National Weather Service (NWS), giving the public little to no time to prepare for safety. This is especially true for the state of California, where scenic coastal views and a desirable Mediterranean climate feed into the common myth that tornadoes do not form in this region, and are therefore not a threat. But tornadoes do form in California; in fact, an average of 11 tornadoes per year are reported throughout the state. This research project analyzes these tornadic events in California, and primarily what differentiates the unwarned tornadoes from those that did receive advanced warning.

Tornado warnings across the state's 58 counties from 2003 to 2012 were compiled, as were all confirmed tornadoes during this ten-year time frame. Case studies of particular storms were chosen based on location, as some counties have a considerably higher occurrence of unwarned tornadic events than others. Synoptic patterns and other necessary parameters for tornado development were compared and contrasted. Radar signatures were chiefly scrutinized, as weak signatures may be a characteristic shared among numerous unwarned California tornadoes.

The influence of terrain and elevation on storm tracks was taken into account with the use of GIS mapping techniques. Factors such as radar location and population density were considered, although the focus of this research project is to gain a better understanding of which atmospheric conditions play a role in the predictability of tornadoes in California. By determining what distinguishes between warned and unwarned tornadoes, this research project will aide in providing more accurate forecasts, which will lessen the likelihood of tornadoes striking California communities unwarned.