fire Article The 2017 North Bay and Southern California Fires: A Case Study Nicholas J. Nauslar 1,2,* ID , John T. Abatzoglou 3 ID and Patrick T. Marsh 2 1 Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK 73072, USA 2 NOAA/NWS/NCEP Storm Prediction Center, Norman, OK 73072, USA;
[email protected] 3 Department of Geography, University of Idaho, Moscow, ID 83844, USA;
[email protected] * Correspondence:
[email protected] Received: 15 April 2018; Accepted: 5 June 2018; Published: 9 June 2018 Abstract: Two extreme wind-driven wildfire events impacted California in late 2017, leading to 46 fatalities and thousands of structures lost. This study characterizes the meteorological and climatological factors that drove and enabled these wildfire events and quantifies their rarity over the observational record. Both events featured key fire-weather metrics that were unprecedented in the observational record that followed a sequence of climatic conditions that enhanced fine fuel abundance and fuel availability. The North Bay fires of October 2017 occurred coincident with strong downslope winds, with a majority of burned area occurring within the first 12 h of ignition. By contrast, the southern California fires of December 2017 occurred during the longest Santa Ana wind event on record, resulting in the largest wildfire in California’s modern history. Both fire events occurred following an exceptionally wet winter that was preceded by a severe four-year drought. Fuels were further preconditioned by the warmest summer and autumn on record in northern and southern California, respectively. Finally, delayed onset of autumn precipitation allowed for critically low dead fuel moistures leading up to the wind events.