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Expert Awareness for Advanced Firefighters & Fire Behaviour Analysts | ||||||
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Studies of deep flaming events have shown the common elements behind their ferocity. In normal fire behaviour we need to consider the residence or burn-out time of a headfire. The distance travelled by the headfire in that time is the flaming depth. Clearly when the FDI and fuel loads are high enough this will produce deep flaming. It is also well established that when a wind change hits a fire, it may activate a flank fire to become a new headfire with significant greater width. This is commonly the result of a cold front hitting a fire driven by pre-frontal weather. Dense spotfires under very low FMC conditions can rapidly amalgamate, producing a high effective rate of spread (although without a headfire). A common mechanism for produce dense spotfires is a fire channelling event. In these the two-directional fire spread makes it a far more effective producer of deep flaming than the other mechanisms. The other major mechanism is abrupt surface drying events, where dry middle level mixes down, either mechanically or through fire forcing. It is the task of Situation Unit analysts to monitor the full set of circumstances. They all involve elevated FDI, and in varying ways strong winds. The terrain aspect of fire channelling is also important. Atmoshperic stability must also be monitored. Any prediction of deep flaming forming must lead to issuing watchouts (Deep flaming) or Red Flag Warnings (Conditions conducive to plume-driven fire). . |