The explicit representation of the atmospheric electric field in numerical weather prediction models is a current challenge. This representation will allow a physically based lightning forecast. Present study aims to assess the performance of the Cloud ELectrification and Lightning Scheme (CELLS) [1] coupled to the Meso-NH atmospheric mesoscale research model [2] in simulating Cloud-to-Ground (CG) flashes. The 17th June 2017 fire events over central Portugal (including the dramatic Pedrogão Grande wildfire) were considered as a real case study. According to an official report of the Portuguese authorities, nine ignition points were reported during that afternoon, some of them caused by lightning. The study discusses the atmospheric conditions that were favorable to lightning flashes production, as well as the possibility to correctly diagnose cloud-to-ground (CG) flashes using high resolution simulations. The simulation was configured with two nested domains of 4 km and 1 km horizontal resolution (Figure 1) and 50 vertical levels, with the innermost domain centred in the area where forest fires occurred. The description of the electrical state of a thunderstorm is based on the monitoring of the electrical charge densities, the computation of the electric field and the production of lightning flashes. The cloud charging involves mostly the non-inductive mechanism, and both Intra-Cloud (IC) and Cloud-toGround (CG) flashes are considered. As shown in [3], the model reproduced an extreme dry thunderstorm environment, responsible for a perfect scenario to natural ignition and fire propagation. The spatial distribution of Meso-NH-CELLS simulated CG lightning showed a good agreement with the lightning flashes obtained from the national lightning detection system.

Predicting the probability of lightning strikes, particularly under very hot weather, can be useful for assess the risk of natural ignitions. The present study aims to assess the performance of the Cloud Electrification and Lightning Scheme (CELLS) [1] coupled to the Meso-NH atmospheric mesoscale model [2] in simulating Cloud-to-Ground (CG) flashes. For this purpose, a simulation of a case study in which many lightning strikes were observed was carried out. The multiple extreme fire event that occurred on June 17, 2017 (including the Pedrogão Grande wildfire) was chosen as case study. According to the Portuguese official report, nine ignition points were reported during that afternoon, some of them caused by lightnings. The simulation was configured with two nested domains of 4 km and 1 km horizontal resolution and 50 vertical levels, with the innermost domain centred in the area where forest fires occurred. The description of the electrical state of a thunderstorm is based on the monitoring of the electrical charge densities, the computation of the electric field and the production of lightning flashes. The cloud charging involves mostly the non-inductive mechanism, and both Intra-Cloud (IC) and Cloud-to-Ground (CG) flashes are considered. The model reproduced an extreme dry thunderstorm environment, responsible for a perfect scenario to natural ignition and fire propagation. The spatial distribution of Meso-NH-CELLS simulated CG lightning showed a good agreement with the lightning flashes observed by the iberic lightning detection system. These results are very promising, indicating the possibility of correctly diagnose lightnings using weather prediction models at high resolutions.

The study aims to assess the applicability of the current Meso-NH electrical scheme (CELLS) in the investigation of forest fire ignition. Therefore, the challenge is to diagnose cloud-to-ground (CG) lightning at 1 km spatial resolution and, subsequently, preferred regions where Forest Fire Events (FFE) could be naturally ignited. The afternoon of 17th June 2017 has been considered for the study, since the dry thunderstorm environment configured a perfect scenario for natural ignition and evolution of some fires. The Pedrógão Grande wildfire ignited in this period and was the deadliest single fire event in the Portuguese history, with at least 60 people killed. The available observational data are used to validate the numerical results and to provide a brief characterization of the meteorological environment when jointly analysed with the simulation. In addition, cloud microphysics and cloud electrical structure are explored from the model results. The spatial distribution of the simulated CG lightning showed a good agreement with the lightning strokes obtained from the national lightning detection network. Overall, this paper introduces a possible application of the Meso-NH electrical scheme, namely the study of forest fire ignition by lightning strokes.