Available research has extensively examined the spatiotemporal patterns of fire‐weather regime in Portugal, but a comprehensive climatology of extreme wildfires is still under development. This study calls for different strategies and scales of analysis aiming to describe the relationships between medium and low troposphere weather conditions and severe fire behaviour in mainland Portugal, between 1980 and 2018. In particular, critical fire‐weather patterns and thresholds that can contribute to operational and forecasting know‐how in short and medium time ranges are presented. We updated the general trends in the fire regime with a new, longer daily burned area series and developed a method that identifies Extreme Wildfire Periods (EWP) that form the basis for climate analysis. Synoptic analysis using Circulation Weather Types (CWT) showed that the northeasterly and easterly directional flows are significantly associated with EWP and produce the most severe fire‐weather conditions. The four main CWT related to extreme fire are driven from anticyclones over the eastern Atlantic between the Azores and the British Isles. However, severe situations can also be regulated by CWT with marginal presence in both summer and EWP: low systems located to the west and northwest of Iberia carrying air masses from the south quadrant are related to catastrophic events. Regarding the antecedent climate, the results indicate that the coincident meteorological drought, whether weak or intense, is a necessary but not sufficient condition for the development of an EWP. An increasing relevance of water stress for shorter intervals preceding EWP, in the order of days and weeks, is apparent. Following these results, fine dead fuel moisture thresholds related to transitions in fire behaviour in Portuguese landscapes are computed using a promising predictive moisture content model. Finally, the different methods used are summoned for the detailed analysis of an EWP starting under unusual synoptic circulation.

Portugal and Spain have a cross-border cooperation protocol on wildfires response for a buffer strip of 25 km for each side of the border. In spite of the success of this collaboration, there are issues to be improved, since Portuguese and Spanish authorities use different methodologies to assess the daily fire danger. A methodology to harmonize fire danger and its interpretation by the Portuguese and Spanish Civil protection authorities in the transboundary buffer strip area is hereby presented. The fire danger index used is the Canadian Fire Weather Index (FWI), which requires input from meteorological data and gives an indication of fire intensity. The fire danger class is an important decision support tool for preventing and fighting wildfires. Since the meaning of FWI values change from region-to-region according to its specific characteristics, a calibration process was performed based on statistical data of the daily FWI values, the number of fires and burned area between 2005 and 2013. The results of the FWI calibration and harmonization of the data for the five danger classes minimizes the fire danger discrepancies across the border. This methodology has the potential to be reproduced in other areas.

Wildfire Decision Support Systems are critical tools for civil protection authorities in the management of all wildfire stages, including prevention. To timely act and apply the necessary preventive measures to reduce the fire danger in wildfires, many proposed calibration studies of the Canadian Forest Fire Weather Index System (CFFWIS) have been performed mainly based on techniques that still depend on manual and empirical analysis, being limited to exploiting a few regions. This paper proposes a methodology for automatic calibration of the CFFWIS to obtain a fire danger measurement that best suits the specific characteristics of a given region. The proposed methodology, applied to 769 regions from Europe, is based on the k-means clustering technique to automatically identify patterns in the data sets composed of elements of the CFFWIS and wildfire records. The results of the automatic calibration of the CFFWIS on each of the 769 regions reinforce the versatility of the proposed methodology, which can be adapted to different regions.

Live Fuel Moisture Content is strongly related to the proneness of live vegetation to ignite and burn, and as such, it is one of the fundamental variables in fire ignition and fire behavior models. While in-situ measurements of this physical variable remain irreplaceable and invaluable, long-term historical records are mostly concentrated in select regions of Mediterranean Europe, United States and Australia. For this and other reasons, there is a strong interest in obtaining estimates based on remotely sensed data on a large spatial scale. To this end, this paper proposes a Live Fuel Moisture Content product based on optical satellite imagery acquired by the European satellites Sentinel-2 and Sentinel-3, and an inversion procedure based on the PROSAIL family of radiative transfer models. An early validation of the product is presented at the S2 and S3 spatial scales using field data provided by the Portuguese Association for the Development of Industrial Aerodynamics of the University of Coimbra and the Institute of BioEconomy of the Italian National Research Council.