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Extreme Wildfire and Microscale Weather Patterns
A Review of Regional and Microscale Weather Patterns Associated with California’s Extreme Wildfires

Dr. Janice Coen presents a look at how weather conditions, at multiple scales from seasonal to microscale, combine to produce some of California’s most destructive wildfire events. The webinar was recorded on August 11, 2021. 

  • Janice Coen, Research Scientist from National Center for Atmospheric Research (NCAR) and University of San Francisco, and Lead of the Pyregence Extreme Weather Analysis Team
  • David Saah, Professor at University of San Francisco and Pyregence Project Principal Investigator

Both historically and in the present, California has been one of the world’s hotspots for extreme wildfire. The state’s Mediterranean climate—characterized by wet winters and hot, dry summers—combines with its complex topography and strong wind events to create rapidly spreading fires. Of particular concern today are destructive wildfires sparked when high winds topple trees and branches onto utility lines.

As part of the Pyregence project, the Extreme Weather Team has analyzed fire activity in recent decades and applied machine learning techniques to identify the extreme weather types (XWTs) that have been associated with rapid fire growth.

Coupled weather–wildland fire behavior simulations of fire events have allowed us understand:

  1. the physical mechanisms that produce fine-scale wind circulations that are not seen in mesoscale forecasts nor in the surface mesonet data
  2. why some fires—only a few percent of all ignitions—grow into megafires.

Simulations of fine-scale airflow in wind-related fire ignition and spread offer new insight into the mechanics, location, and predictability of under-recognized microscale wind extremes and fire-induced winds that can elevate maximum speeds well beyond those anticipated in electrical grid design.