Let’s focus on the biggest of the big:
- August Complex; California; August 17, 2020; 1M acres; 900 structures
- North Complex; California; August 17, 2020; 318K acres; 2500 structures
- Marshall; Colorado; December 30, 2021; 6K acres; 1100 structures
- Lahaina; Hawaii; August 8, 2023; 2K acres, 2000 structures
- Eaton; California; January 7, 2025; 14K acres, 9400 structures
- Palisades; California; January 7, 2025; 23K acres; 6800 structures
Combined, approximately 150 fatalities. And truly heartbreaking.
Do they have anything in common?
Absolutely. There are two groupings in the data:
1) the two lightning-based California complexes
2) the other wind-based fires
California Lightning Complexes
The California complex (“Complex” means multiple fires in same area or merging into larger fire, frequently with same Incident Command), were started by lightning (dozens of lightning strikes ignited) into dry fuel, and surrounded by dead & dying trees. There was strong wind which helped spread fire, but not in the same way as the other 4 fires on the list. These fires were relatively remote and numerous and gave no possibility of success of “initial attack”.
These two complexes lasted months, putting very large burn scars across the forests, and sending significant amounts of smoke into the atmosphere.
The other fires ignited in very strong wind during atypical dryness.
The Marshall fires occurred during dry 70+ MPH winds (sometimes called Chinooks) that usually take place in the moister winter conditions. The year of 2021 was the driest summer & fall (compared to the amount of rain during spring) in the 150 year history of records at the Boulder NWS. This lead to a healthy grass crop from the spring rain. But that grass became bone dry. Then came the extremely strong winds, and an ignition upwind from a community.
Other wind-drive fires
The Lahaina fire was very similar to Marshall. August 8th had likely the strongest dry winds seen in Hawaii in the past 50 years, coupled with very dry conditions (exacerbated by the downslope forces in West Maui). Add to that, the community of Lahaina now has a large pasture of invasive grass upwind from their community (formerly plantations). This grass dries out quickly and burns very hot, and tends to throw embers in the wind. It was almost certainly the strongest dry wind in Maui since the plantations were removed, leaving fuel that fed right up to the community.
Both the Eaton and Palisades fires have a similar story to Marshall and Lahaina. Southern California had some of the lowest rain totals in decades. The local shrubs and grass were extremely dry. Then came very strong winds. The winds were not as record breaking as Lahaina (relative to their local history) but they aligned with the dryness to create catastrophic fire weather.
Santa Ana winds in Southern California (winds that blow dry air over the mountains from the northeast) can occur between September and February, but usually rain has fallen by December.
Conclusions
Over the next week, each of these fires will have Case Studies in the PyroBlog with more in depth discussion and data/graphics.
The first lesson is that Wildfire risk usually takes multiple bad events to occur at the same time (wind, dryness, location of ignition). Utilities can be aware of the severity of fire weather. And most utilities do not need sophisticated and expensive data to be “situationally aware”.
The second lesson is that severe wildfire risk is limited to a small number of days. Reviewing the PRZ map, the redder the area the more days per year.