Strong convective winds and high-impact events cause significant damage to buildings, infrastructure, and forests, which we analyse using high-resolution satellite and orthophoto maps. We focused on three episodes that occurred in the Balearic Islands, located in the western and (iii) Mallorca Island on 29 August 2020. We analyse changes in the land cover using vegetation index calculated before and after each event allow us to identify damage in forested land cover. We tested three different temporal windows: 2, 6, and 12 months. In general, we obtained the best results using images taken 6 months after each event, compared to the images taken just before the event occur. Furthermore, we conducted an analysis of the wind-thrown tree direction patterns. We compared the observed patterns in orthophoto maps with those derived from an idealized tornado-like vortex (Rankine vortex). The results confirm all three events were single tornadoes, whereas no downburst-related damage patterns could be clearly identified. We also investigated how complex orography features interact with wind-related forest disturbances. Our research showed that trees are more likely to be damaged on mountain slopes that face the wind and at the bottom of valleys that are oriented perpendicular to the storm's path. Conversely, damage gaps typically occur downwind, particularly to the leeward side of cliffs. Lastly, we estimated the dimensions of damage paths using orthophoto maps, resulting in lengths exceeding 10 km for all the cases (only 7% of reported tornadoes in Spain exceed this threshold according to previous studies) and maximum widths greater than 1 km. In fact, the Mallorca 2020 tornado's damage swath width reaches a width of 2.8 km, making it the widest ever reported in the Balearic Islands and in Spain; it is also one of the widest in Europe, according to historical records.
This article presents the first climatology of severe thunderstorms (STs) in the Balearic Islands, Spain, between 2010 and 2023. The criteria used to classify severe thunderstorms in the database are as follows: straight-line winds exceeding 90 km/h, hail with a diameter of 2cm or more or a tornado touching the ground. Meeting any one of these three crireria was sufficient for a thunderstorm to be classified as severe. Thanks to severe weather reports, observations from 111 weather stations and additional data sources, an exhaustive database of STs in the Balearics was constructed, including 43 severe thunderstorms affecting the islands during 41 severe thunderstorm days. The database itself is included in this paper, and is accessible to the scientific community, representing the first contribution of this paper. A second contribution is a detailed analysis of the spatial and temporal distribution of STs affecting the Balearic Islands. Annual, monthly, seasonal, fortnightly, spatial and hourly distributions were studied. Autumn accounts for 48.8% of all STs, with the highest frequency observed in October. The fortnightly distribution revealed a peak of 7 STs during the second half of August. Convective straight-line winds were the most common severe phenomena in STs affecting the Balearic Islands, occurring in 41.9% of all cases. The hourly distribution showed a peak between 10:00 and 12:00 AM. In terms of spatial distribution, the highest incidence was recorded on the largest island, Mallorca, with a mean of 2.6 STs per year. The southern region of Mallorca, followed by its central part, emerged as hotspots for severe thunderstorms within the archipelago. The vast majority (84%) of the registered STs in the islands originated offshore. For this reason, another key contribution of the paper is the analysis of the relationship between ST frequency and sea surface temperature (SST) and SST anomalies. For each severe thunderstorm day, the mean SST and SST anomaly in the Balearic Sea were obtained using daily reanalysis at 12 UTC from ERA5. Peak ST activity occurred when SST ranged between 25 degrees C and 26 degrees C. Extremely severe thunderstorms (ESTs), defined by wind gusts over 120 km/h, hail of 5 cm or more, and/or a land tornado rated EF1 or higher, occurred most frequently when SST ranged between 27 degrees C and 28 degrees C.
This work aims to evaluate the performance of outputs in six regional climate models (RCMs) of 17), at the Medjerda Watershed. It is based on the evolution of precipitation during the reference the root mean square error (RMSE), the percentage of bias (P BIAS), the Taylor Diagram and Taylor's Skill Score (TSS)). The results confirm the difference between the RCMs in the estimation of climatic variables at different time scales (annual, seasonal and monthly). The annual precipitation regime has been accurately predicted by REMO2009, which presents a result of 0% in terms of P BIAS between observations and simulations. The agreement between the observed and simulated precipitations at a seasonal time scale is superior in terms of the correlation r = 1 by REMO2009, RACMO22T, CCLM4-8-17, CRCM5, HIRHAM5. In terms of RMSE the REMO2009 model scored a low value of 1.13 mm in autumn, on a monthly time scale, while the CCLM4- 8-17 model showed a high performance value in terms of Taylor's Skill Score (TSS = 0.91). In overall terms, those models, which reproduce the observed climatology of the Medjerda basin more efficiently, and which may be considered the most efficient, include REMO2009, CCLM4-8-17, RACMO22T and CRCM5. This study recommends the use of these selected models for future precipitation projections in the Medjerda Watershed and it is therefore necessary to correct the outputs of the regional models of the Cordex-Africa project and to use the set of those models that perform most efficiently with respect to future climate change impacts and for adaptation studies on the African continent.
This study seeks to estimate the precision of three different high-resolution atmospheric models in the simulation of two sets of short-term weather forecasts for a duration of two-weeks for the Italian Peninsula. The following models were used: WRF (Weather Research and Forecasting Model), COSMO (Consortium for Small-scale Modelling) and ICON (Icosahedral Nonhydrostatic Model). The capability of these weather forecasting systems has been evaluated using their optimum-configurations, which were obtained from a tuning procedure at a spatial resolution of about 2 km over Italy. The models share the same forcings given by the Integrated Forecasting System (IFS) analyses provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) with a grid-point distance between neighbouring points of approximately 0.081 & DEG; (& SIM;9 km). This study was performed over two periods: from 01/01/2019 to 15/01/2019 and from 16/08/2020 to 30/08/2020. These periods were chosen to characterise the models' performance over the winter and summer seasons respectively. The precision of these weather forecasting systems were evaluated by taking their best-configurations, which were obtained from a tuning procedure at a spatial resolution of 0.018 & DEG; (& SIM;2 km) over the domain specified. The ERA5-Land reanalysis, which was provided by the Copernicus Climate Change Service (C3S) and the gridded SCIA observed data (SCIA -Sistema nazionale per la raccolta, elaborazione e diffusione di dati Climatologici di Interesse Ambientale). The results for each model reveal that the variables analysed here are all consistent with respect to those observed, as they capture the main features that characterise the summer and winter weather conditions investigated here. Those differences observed among the models may be related to the complex parameterization schemes used in WRF, COSMO, and ICON, that could affect the models' performance.
The Radar Network of the Meteorological Service of Catalonia provides volumetric coverage of the entire region of Catalonia. With respect to the Pyrenees, this network allows us to identify the complete life cycle of thunderstorms accurately, despite low level beam-blockage caused by topography. This research paper focuses on convection initiation, and considers that only those cases of diurnal evolution selected, and the first daily thunderstorm. The spatial distribution of the first daily convective echoed in the Western and Eastern Catalan Pyrenees reveals obvious differences, with a predominance of the second sector. Furthermore, as the reflectivity threshold used increases, the differences between both areas also rise. The selected discriminating reflectivity values used in the analysis were 15, 35 and 45 dBZ, and correspond to weak, moderate, and heavy precipitation. However, this difference arises from the influence of the county of El Ripolles, where over 30% of the initial convection for all three reflectivity thresholds occurs. Finally, a high spatial resolution analysis has allowed us to detect how the northern part of the abovementioned county is the most relevant hotspot in terms of initial convection in the Catalan Pyrenees.
