From the Largest California Wildfire to Major Post-Fire Debris Flows in One Month; Communicating the Unique Threats for Back-to-Back Disasters (87)

Eric Boldt, NOAA/National Weather Service, Oxnard, CA



The Los Angeles/Oxnard National Weather Service (NWS) Office provides critical Decision Support Services (DSS) for its partner fire agencies and emergency managers responsible for preparing for and responding to potentially catastrophic wildfires. The 2017 fire season in southern California was especially active, with five different fires exceeding 5,000 acres in size and topped by the largest wildfire in California recorded history, the Thomas Fire (281,893 acres) that began on December 4, 2017. Despite these fires burning over 300,000 acres and threatening tens of thousands of structures, fatalities were limited to two (Thomas Fire) individuals with less than a thousand residences destroyed. The preparedness activities and DSS quickly changes gears after wildfires when heavy winter rains can generate devastating debris flows from the recent burn scars.

The threat of major debris flows moved closer to reality when the NWS forecast that intense rain would impact the area January 8-9, 2018, even while the Thomas Fire continued to burn. Thousands were evacuated during the fire, but would the public be motivated to evacuate a second time in a month for a lesser known although equally dangerous hazard? Even though the NWS provided aggressive DSS well in advance of the storm and critical partners gave evacuation orders a full day ahead, the public perception of a life-threatening debris flow was not at the same level as the wildfire. Tragically, an extreme debris flow occurred from the Thomas Fire burn area on the early morning of January 9, resulting in 21 fatalities (with 2 people still missing) in Montecito, California. Extensive agency partnerships and the resulting response likely saved many lives in this case, yet the event demonstrates the importance of exploring innovative ways to prepare for these complex and potentially devastating hazards to save even more lives.

Eric Boldt: Warning Coordination Meteorologist, NOAA/National Weather Service Los Angeles/Oxnard, 520 North Elevar Street, Oxnard, CA 93030. 805-988-6623