The Synoptic and Mesoscale Evolution Accompanying the 2018 Camp Fire of Northern California

Abstract

AbstractThe Camp Fire event was associated with dry, northeasterly winds that descended the western slopes of the Sierra Nevada of Northern California during the early morning hours of 8 November 2018. The downslope winds peaked around sunrise, with strong winds pushing the fire rapidly toward Paradise, California. Similar to recent central/Northern California wildfires associated with downslope winds, the synoptic pattern was characterized by building sea level pressure over the Intermountain West and a trough along the coastal zone, with both the synoptic evolution and low-level winds skillfully forecast by operational models. The maximum wind gusts along the western Sierra Nevada slopes ranged from 10–20 kt (1 kt ≈ 0.51 m s−1) at sheltered locations to 50–60 kt at exposed sites on the mid- to upper slopes of the barrier. The highest winds were not climatologically exceptional, and low-level temperatures were cooler than normal over and to the east of the Sierra Nevada, near normal over the western slopes, and warmer than normal over coastal California. Drier-than-normal conditions prevailed during the ∼3 days preceding and during the event, as a result of downslope winds. The origin of the fire can be traced to strong winds interacting with a failing electrical transmission infrastructure, with highly flammable surface fuels fostering rapid fire movement between the ignition source and Paradise.