This sounds like an Extreme Wildfire Event (EWE) in the lingo we are all going to be hearing more of:
In the current technological conditions, the accepted limit of capacity to control a fire is 10,000 kWm−1. Beyond 10,000 kWm−1, it is well accepted that even heavy water bombers are ineffective, and fire control is not possible with current day technology and technical resources. Long flames also make fires increasingly difficult to control and represent a threat for firefighters who must operate approaching to fire front, but respecting their “safety zone”. With an increasing FLI, the quantity of water to be eventually used as an extinguishing agent to contain flames grows. When FLI is close to the 10,000 kWm−1 threshold, the water amount needed to contain flames is evaluated in 25 to 30 liters every 30 seconds per meter of front...
...EWE is defined as:
a pyro-convective phenomenon overwhelming capacity of control (fireline intensity currently assumed ≥ 10,000 kWm−1; rate of spread >50 m/min), exhibiting spotting distance > 1 km, and erratic and unpredictable fire behavior and spread. It represents a heightened threat to crews, population, assets, and natural values, and likely causes relevant negative socio-economic and environmental impacts.
https://res.mdpi.com/d_attachment/fire/ ... 009-v2.pdfThe crucial measure seems to be fireline intensity (FLI). Once that is over 10000 kW/m, then the fire cannot be controlled. Alberta’s Chisholm fire was an EWE with an FLI of 233,000 kw/m.