Type U3. Pyro-puff (isolated towering pyro-Cu)
If one of more fire Sectors make hot uphill runs, causing mixing down of dry air aloft, increasing fire intensity during the run, a short-lived form of VPC may occur. The resulting feedback does not persist when the uphill run ends. Potentially, burn-out ignition patterns could be involved, via a high isoperimetric ratio (the ratio of a fire’s basal perimeter to its area). If this is possible, then such ignitions should be halted immediately. Short-lived (under 30 minutes generation time above fire) towering pyroCu, minimum average cloud-top temperature typically above -40°C.The duration of core plume generation is less than the time taken for the plume to reach maximum altitude.
Normal fire ground safety protocols should apply during such hot uphill runs, with monitoring for enhanced feedback developing.
