Climate links to escaped prescribed fires in California and Nevada

Investigations into management-ignited fires (prescribed burns) that escape control and become wildfires frequently point to drought conditions as a contributing factor in the escape. We correlated escaped fire area burned in northern California and Nevada from 1982-2002 to the Palmer Drought Severity Index (PDSI) to determine whether drought conditions occurred concurrently with extensive escaped prescribed burns in this region. We found that years with the greatest area burned totals corresponded to years when PDSI was strongly positive, indicating conditions were wetter than average. Additional analysis of large escaped prescribed fires (>200 ha) revealed that the largest escapes not only occurred under significantly wetter climatic conditions than smaller escapes, but occurred during the fall months on days when NFDRS fire danger values were low or average. Since these findings were contrary to the investigations and commonly held perceptions about drought and escaped fires, we then assessed fifteen of the largest escaped prescribed fires individually to determine common meteorological patterns conducive to escaped fires. This paper discusses the results of the study and offers management implications of the findings.