Wildfire is one of the most complex natural hazards. Its origin is a combination of anthropogenic factors, urban development and weather plus climate factors. In particular, weather and climate factors possess many spatiotemporal scales and various degrees of predictability. Due to the complex synergy of the human and natural factors behind the events, every wildfire is unique. However, there are indeed common meteorological and climate factors leading to the high fire risk before certain ignition mechanismfigures occur. From a scientific point of view, a better understanding of the meteorological and climate drivers of wildfire in every region would enable more effective seasonal to annual outlook of fire risk, and in the long term, better applications of climate projections to estimate future scenarios of wildfire. This review has performed a comparison study of two fire-prone regions: southeast Australia including Tasmania, and the Adriatic coast in Europe, especially events in Croatia. The former is well known as part of the ‘fire continent’, and major resources have been put into wildfire research and forecasting. The Adriatic coast is a region where some of the highest surface wind speeds, under strong topographic effect, have been recorded and, over the years, have coincided with wildfire ignitions. Similar synoptic background and dynamic origins of the meso-micro-scale meteorological conditions of these high wind events as well as the accompanied dryness have been identified between some of the events in the two regions. We have also reviewed how the researchers from these two regions have applied different weather indices and numerical models. The status of estimating fire potential under climate change for both regions has been evaluated. This review aims to promote a global network of information exchange to study the changing anthropogenic and natural factors we have to confront in order to mitigate and adapt the impacts and consequences from wildfire.

The Split wildfire in July 2017, which was one of the most severe wildfires in the history of this Croatian World Heritage Site, is the focus in this study. The Split fire is a good example of a wildfire–urban interface, with unexpected fire behavior including rapid downslope spread to the coastal populated area. This study clarifies the meteorological conditions behind the fire event, those that have limited the effectiveness of firefighting operations, and the rapid escalation and expansion of the fire zones within 30 h. The Split fire propagation was first reconstructed using radio logs, interviews with firefighters and pilots involved in the intervention, eyewitness statements, digital photographs from fire detection cameras, media, and the monthly firefighting journal. Four phases of fire development have been identified. Then, weather observations and numerical simulations using an enhanced-resolution operational model are utilized to analyze the dynamics in each phase of the fire runs. The synoptic background of the event includes large surface pressure gradient between the Azores anticyclone accompanied by a cold front and a cyclone over the southeastern Balkan Peninsula. At the upper level, there was a deep shortwave trough extending from the Baltic Sea to the Adriatic Sea, which developed into a cut-off low. Such synoptic conditions have resulted in the maximum fire weather index in 2017. Combined with topography, they also locally provoke the formation of the strong northeasterly bura wind along the Adriatic coast, which has been accompanied by a low-level jet (LLJ). The bura (downslope wind), with mid- to low-level gravity-wave breaking and turbulence mixing (as in the hydraulic jump theory), also facilitated the subsidence of dry air from the upper troposphere and rapid drying at the surface. This study demonstrates that numerical guidance that indicates the spatial and temporal occurrence of a LLJ is highly capable of explaining the Split fire evolution from the ignition potential to its extinguishment stage. Thus, in addition to the conventional fire weather indices, such products are able to improve fire weather behavior forecasting and in general more effective decision-making in fire management.

In Europe, forest fires are a serious and constant threat. They destroy forests and forest land, causing damage, financial loss, and long-lasting impacts on forest ecosystem services. There are several ways to decrease the number of forest fires, including continuous investment in fire prevention measures and the intensive implementation of adaptive sustainable forest management measures, which need additional financial resources. In many cases, forest management activities in karst forests are not implemented in a timely manner and in coordination with other stakeholders. A comprehensive study about the impact of forest fires on different economic activities (tourism and protected areas) is not currently available. In this study, the legislative framework in Croatia was analysed in relation to the fire protection activities and jurisdictions of different institutions. From data collected in the period 2013–2020, the first-age class afforestation costs and growing stock assortment value were calculated, and the non-wood forest functions were estimated. The aforementioned data were further compared to the Fire Weather Index (FWI) and Seasonal Severity Rating (SSR) of fire seasons. The total estimated damage is EUR 326,810,724.72. The research emphasises the need for the implementation of cross-sectoral forest policy measures. The state forest company should allocate more financial resources for biological forest restoration in the future. Forest management practices should implement climate-adaptable silviculture measures to preserve forest and forest land.

Understanding the relationship between fire behavior and the driving weather conditions is critical for fire management and long-term fire risk assessment. In this study, we focus on two wildfire events: the Split wildfire in Croatia and the Forcett–Dunalley wildfire in Tasmania, Australia. The antecedent weather in both events included extremely dry conditions and higher-than-average air temperatures in the months prior to the events. The synoptic patterns in both events consisted of a large surface pressure gradient, which generated strong wind, driving the fire’s spread. The Weather Research and Forecasting (WRF) model was utilized to simulate fire weather conditions during the development of the two events. In the innermost domain of WRF, resolution is 500 m with explicit moisture calculation only, and there are 66 vertical levels, with about 20 of them to resolve the boundary layer. The WRF simulations are well verified by station observations, including upper-level wind speeds. The convergence line pattern in the Tasmanian event, which was conducive to intense plume development, has been well simulated. Only a slight discrepancy was identified in the simulation of the coastal change in wind direction in the Croatian event. It is identified that in the Split case, bura wind was highly coupled with an upper-level trough, which induced subsidence of the upper-level dry and cold air to the surface, causing rapid drying of the fuel. During the Forcett–Dunalley fire, the atmosphere was unstable, which enabled deep pyrocumulonimbus development. In general, the development from ignition to the timing of the most extreme fire intensity in both events was largely determined by the evolution of the surface to upper-level meteorological drivers. While these extreme meteorological conditions would impact fire-fighting strategies such as aircraft operations, a model-based estimate of the high-risk areas is critical. Our findings would also benefit an estimate of the climatology of fire events with similar behavior and thus a long-term fire risk assessment.

A major bushfire occurred during January 2013 near the towns Forcett and Dunalley in southeast Tasmania, Australia. Several records were broken by this wildfire, in terms of impacts to eco-systems, infrastructure and lives, and it was the first pyrocumulonimbus documented in Tasmania. The Australian Bureau of Meteorology high-resolution regional reanalysis for Tasmania (BARRA-TA), with 1.5-km spatial resolution, together with in-situ observations, was applied to reconstruct the wildfire event. The antecedent climatic conditions in Tasmania included a large increase in fuel load due to abundant rain one to two years before the event, followed by a heatwave during the summer of 2012/13. In the three periods we identified during the event reconstruction, the second period was the most dramatic, in which a low-level jet was directed downslope in southeast Tasmania to accelerate the fire spread. The BARRA-TA reanalysis revealed the mesoscale features occurring during the fire event additional to the climatic conditions and synoptic patterns documented in past studies. These include a cold front that crossed the fireground during the third period, and thus played a different role compared with some past extreme fire events in terms of airmass lifting and wind direction change. Moreover, mid-level moisture advected into the area was conducive to pyroconvection development.

The Weather Research and Forecasting Spread FIRE (WRF-SFIRE) model was used to simulate the evolution of the fire perimeter for the Split wildfire in Croatia, evaluated in our previous detailed reconstruction of the event. A four-domain configuration was applied, with the innermost domain having a resolution of 500 m with a planetary boundary layer parameterization. The coupled fire grid was further downscaled to 33.3-m resolution, using the best available estimates of topography and fuel load data. WRF-SFIRE simulated slightly smaller fire areas in the four observed fire perimeter stages of the Split wildfire event, especially the northwestward spread in the last stage along the Adriatic coast. Additional experiments with multiple ignitions in the WRF-SFIRE model, representing the spotting mechanism, successfully simulated the northwestward spread in the event. The study also included sensitivity experiments that turned off the heat and moisture flux coupling between WRF and the fire grid. It was found that the simulated fire area is larger than the model run that included heat and moisture feedback from the fire grid to the atmosphere, which is contrary to some previous studies. The large wind speed and convergence along the fire line in our feedback-on simulation, which constrain the fire when there are feedback processes, were likely the cause of the smaller fire area. Last, areas of pine that burnt in the Split fire event favored crown fire spread, which is not represented in the current modeling framework of WRF-SFIRE.