The fire that occurred in the Serra da Lousã on July 11, 2020 resulted in the death of one firefighter and the injury of three other firefighters. It was considered that the fire would have started due to an electrical discharge associated with a thunderstorm and that the accident with the firefighters would have been related to a change in the direction of the wind, having also been reported the existence of a lot of smoke close to the ground. These possibilities were analyzed by IPMA through the assessment of weather conditions on the day of the fire.
The fire occurred on a day for which hot and thunderstorm meteorological warnings were issued, with strong atmospheric instability and the consequent generation of a strong convective system. The meteorological risk of fire was very high in the municipality of Lousã, the 4th highest level of a total of 5 levels.
A record of an atmospheric electrical discharge was identified at 18:20 local time (17:20 UTC), 100 m from the fire site, and the margin of error associated with this electrical discharge (in the order of 200 m) allows inferring that this discharge may have triggered the Lousã fire. This observational evidence is further supported by numerical modelling data.
It was also possible to identify that the convective system where the aforementioned electrical discharge originated produced, even during its movement towards the north and in the dissipation phase, a generalized subsidence in the fire region, consistent with the decrease in the height of the boundary layer, which may have relevant to the difficulty in dispersing fumes and gases close to the ground.
It is also not possible to exclude that during the period of time between the start of the fire and the moment when the accident with the firefighters occurred, significant variations in the wind direction may have occurred, consistent with the existence of downward currents associated with the convective cells that constituted the convective system, which influences both the evolution of the fire and the fumes it produces.
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