It is currently assumed that anthropogenic climate change has differentially altered the probabilities of extreme events occurring in the development of certain meteorological phenomena, such as temperatures and precipitation, in many regions of the planet. But, there is little or no consensus on its impact on African Dust Outbreaks (ADO). The objective of this study was to estimate the contribution of global warming (thermodynamic factors) and of changes in certain atmospheric circulation types (CT, dynamic factors) to the detected increase in the development of ADO over areas of Spain (Salvador et al., 2022).

To this end, values of daily probability of ADO occurrence (PROB-ADO) over eight regions of Spain in 1940-2024, were calculated with numerical prediction models (Salvador et al., 2024). ERA5 daily fields of temperature and geopotential height at different levels were used to calculate the thermodynamic parameters that feed the models and to generate daily synoptic CT maps at 850 hPa at 12 UTC. PROB-ADO extremes were thus defined as days on which PROB-ADO exceeded the 90^th percentile of the time series of daily values for the period 1940-2024.

Then, a circulation classification methodology was applied to group all days of this period into one of the 11 characteristic CTs identified by Salvador et al. (2022). Six out of the 11 patterns, were identified as ADO-CTs.

To calculate temporal trends in the time series of annual frequencies of the 11 CTs and of values of PROB-ADO and PROB-ADO extremes over 1940-2024, the Theil-Sen methodology was used. Finally, to determine the dynamic, thermodynamic and interactive contributions of each individual CT to the general trend in the occurrence of PROB-ADO extremes, the quantitative partitioning methodology proposed by Horton et al. (2015) was applied.

Statistically significant increasing trends in PROB-ADO extremes were obtained in all 8 zones for the period 1940–2024. Trend estimators ranged from 0.016 days/year in the NW zone to 0.628 days/year in the SE. There was a clear decreasing gradient along the SE-NW axis. Thermodynamic contributions were predominant, ranging from 41% in the NW to 94% in the SE sector. The dynamic contribution was smaller and varied between 9% in the SE zone and 47% in the NW. Mixed contributions were very small, ranging from -4% to 12%, and are mostly negative, indicating that this type of interaction didn’t contribute to an increase in the trend for PROB-ADO extremes. The largest overall contribution (increases of between 0.01% and 0.18% of the days in the year) came from ADO-CT1 (between 31% and 67% of the trend) and, to a lesser extent, ADO-CT6 (between 10% and 31%). Our results indicate that although a substantial portion of the observed change in PROB-ADO extremes has resulted from thermodynamic changes, it has also been altered by recent changes in the frequency of ADO-CTs.

Acknowledgements

This research received support from MITECO and from project POSAHPI-2 (ref. PID2022-143146OB-I00).

References

Horton, D.E. et al., 2015, https://doi.org/10.1038/nature14550.

Salvador, P. et al., 2022, https://doi.org/10.1038/s41612-022-00256-4.

Salvador, P. et al., 2024, https://doi.org/10.1016/j.scitotenv.2024.171307.

How to cite: Salvador, P., Scofield, D., Pey, J., Pérez, N., Alastuey, A., Querol, X., and Pujadas, M.: Recent trends in probability of African dust outbreaks occurrence over Spain: Quantitative partitioning of dynamic and thermodynamic effects., 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-13, https://doi.org/10.5194/egusphere-plinius19-13, 2026.

Large-scale atmospheric circulation exerts a primary control on environmental variability over the western Mediterranean, where African dust outbreaks strongly affect aerosol loading, radiative balance, air quality, and ecosystem dynamics. Although recent decades have shown substantial interannual variability in African dust transport towards Iberia and the Mediterranean Basin, uncertainties remain regarding the long-term evolution of dust-favourable synoptic conditions under climate change. Here we investigate the past, present, and future evolution of atmospheric circulation regimes associated with African dust outbreaks using a multi-source framework that combines reanalysis datasets, CMIP6 climate simulations, observational dust records, and sedimentary archives.

Daily atmospheric circulation states were characterised using 850 hPa geopotential height fields over North Africa and the western Mediterranean. We applied a fixed-centroid weather-regime classification consistently across modern reanalyses, long-term historical reconstructions, and climate model simulations. The classification identifies 11 recurrent synoptic circulation regimes, of which 6 are significantly associated with enhanced African dust transport towards Iberia and the western Mediterranean (Salvador et al, 2022). Dust relevance was validated using independent observational datasets, including satellite-constrained aerosol products and observational catalogues of African dust outbreaks over the Iberian Peninsula.

To extend the analysis beyond the satellite and modern observational period, we incorporated long-term reanalysis products such as the NOAA 20th Century Reanalysis, allowing reconstruction of circulation variability back to the 19th century. This enabled us to assess whether the recent increase in dust-favourable circulation patterns is unprecedented within the context of the last ~200 years, and to evaluate multidecadal variability linked to large-scale modes of atmospheric circulation. We further compared these reconstructed circulation trends with historical simulations from CMIP6 models.

Multi-model ensembles are then used to assess future changes under SSP1-2.6 to SSP5-8.5 scenarios. Preliminary results show that dust-related circulation regimes represent ~58% of days in the historical baseline period (1980–2014). Both ERA5 and the CMIP6 historical ensemble show positive trends in dust-favourable circulation occurrence (~+0.69% and +0.67% per decade, respectively). Future projections indicate a robust intensification of these conditions throughout the 21st century, particularly under high-emission scenarios. Under SSP5-8.5, trends reach nearly +1.94% per decade, suggesting a substantial increase in the persistence and recurrence of atmospheric configurations conducive to African dust transport. Results also indicate a seasonal expansion of dust-conducive circulation into spring months.

Additionally, we intend to explore the feasibility of using sedimentary evidence of African dust deposition in lacustrine archives from the Iberian Peninsula and the Pyrenees. These high-resolution sediment records may provide an independent paleoclimatic benchmark to evaluate the realism of reconstructed atmospheric circulation and inferred dust variability over longer timescales. Ongoing analyses include hyperspectral imaging, geochemical tracers, and mineralogical indicators associated with North African dust inputs. By integrating atmospheric dynamics, climate model simulations, historical reanalyses, and sedimentary evidence, this work aims to improve the diagnosis and long-term understanding of extreme aerosol transport events in a changing climate and to provide a more robust framework for evaluating future dust-related hazards in the Mediterranean region.

How to cite: Scofield-Teruel, D., Salvador, P., Valero-Garcés, B. L., and Pey, J.: Past and Future Changes in African Dust-Favourable Atmospheric Circulation over Iberia, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-22, https://doi.org/10.5194/egusphere-plinius19-22, 2026.

Heatwaves (HWs) are among the most damaging climate extremes affecting the Mediterranean basin, where they could drive excess mortality, agricultural losses, water stress and wildfire risk. The Mediterranean region is warming fast, and the frequency, duration and intensity of HWs are projected to keep rising. Anticipating these events requires understanding their drivers. The complex interaction between large-scale atmospheric circulation, remote teleconnections and local land-surface conditions is difficult to capture with conventional statistical or dynamical approaches, and these drivers may vary markedly from one Mediterranean sub-region to another.

This work proposes the application of a general driver identification framework, Spatio-Temporal Cluster-Optimized Feature Selection (STCO-FS), to identify the key short-term and seasonal drivers of HWs across the Mediterranean basin. The method combines clustering algorithms for reducing the spatial dimensionality with an ensemble evolutionary optimization algorithm to perform driver selection jointly in the spatial and temporal domains. In a first phase, gridded predictor fields from the ERA5 reanalysis, such as mean sea level pressure, geopotential height at 500 hPa, sea surface temperature, soil moisture, total precipitation and 2 m temperature, are reduced in dimensionality by grouping grid points with similar temporal behaviour into clusters. Climate variability indices (e.g. NAO, ENSO, IOD) and local variables are added directly. In a second phase, a wrapper feature selection approach based on a multi-method evolutionary algorithm (PCRO-SL) selects the most skilful drivers and identifies, for each one, the optimal time lag and time window, distinguishing short-term precursors (days) from sub-seasonal and seasonal influences (up to several months) of HW occurrence.

The framework will be evaluated on representative areas of the Mediterranean. We expect that this approach will allow us to unravel the relative contribution of the different variables, and to characterise how these contributions differ across sub-regions of the basin. By revealing the spatio-temporal structure of HW drivers, this framework aims to improve the physical understanding and sub-seasonal predictability of Mediterranean HWs, supporting more effective early warning and climate adaptation strategies.

How to cite: Pérez-Aracil, J., Peláez-Rodríguez, C., McAdam, R., Squintu, A., Cornejo-Bueno, L.-M., Scoccimarro, E., Luterbacher, J., Giuliani, M., Xoplaki, E., Castelleti, A., and Salcedo-Sanz, S.: Identifying the spatio-temporal drivers of Mediterranean heatwaves: a machine learning feature selection framework, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-89, https://doi.org/10.5194/egusphere-plinius19-89, 2026.

Evidence of global warming is clearly reflected in extreme daily maximum temperature events, particularly when record-breaking temperatures occur. In the Iberian Peninsula, previous studies showed that the frequency of such records exhibits a non-stationary behaviour, with an upward trend and strong spatial variability. In this work, we build a statistical model to explore and interpret the spatial heterogeneity and spatio-temporal structure of this phenomenon.

Daily maximum temperature (T_x) series from 36 meteorological stations across Spain covering the period 1960-2023 were obtained from the European Climate Assessment & Dataset. Predictor variables were obtained from ERA5 reanalysis data, consisting of geopotentials at 300, 500, and 700 hPa at 12:00 UTC, covering a 1º x 1º grid spanning [45º N, 10º W, 35º S, 5º E]. The analysis was restricted to the summer season (JJA).

A previously developed modelling framework was applied to obtain station-specific logistic regression models, as well as global models. The response variable was defined as a binary indicator of extreme heat event (EHE) occurrence. For each station s, the event threshold was defined as the 95th percentile of T_x in the reference period 1981-2010, computed over summer days only. Formally, the threshold is given by u_s = Q_0.95 (T_x,t,l t ∈ [1981, 2010], l ∈ [1, 92]) where T_x,t,l denotes the daily maximum temperature at station s on day l of year t. An EHE is then defined through the indicator I_x,t,l = 1 if T_x,t,l > u_s , and 0 otherwise, with value 1 indicating the occurrence of an EHE.

The modelling strategy was carried out in three steps: (1) stepwise logistic regression was performed independently at each station to identify relevant predictors; (2) the most frequently selected and influential variables across stations were used to construct a global model; and (3) three extended models were developed by incorporating interactions with geodesic, climatic, and spatial covariates, followed again by stepwise selection. The first 51 years of the period were used for building the models and the final 13 years were reserved for validation. Due to class imbalance, model performance was evaluated using the AUC measure.

The best results were obtained from the global model including climatic interactions, which reached an AUC of 0.89 with k = 34 parameters and was therefore selected as the winning model. The individual geopotential terms of this model were analysed to better understand the climatic characteristics associated with EHEs. It was also used to simulate EHEs over the validation period. The simulated EHE sequences were compared with the observations in order to evaluate the model’s ability to reproduce consecutive-day heatwave dynamics. In addition, the model’s assigned probabilities of EHE occurrence were assessed during selected heatwave episodes in the validation period.

How to cite: Barrio-Torres, E., Gracia-Tabuenca, Z., Castillo-Mateo, J., Asín, J., Cebrián, A. C., and Abaurrea, J.: Statistical Modelling of Extreme Heat Events Using Geopotential Height Covariates, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-37, https://doi.org/10.5194/egusphere-plinius19-37, 2026.

Mediterranean heatwaves are among the most impactful extreme weather and climate phenomena, with significant impacts on human health, ecosystems, energy demand, and water resources. The Mediterranean basin is widely recognized as a climate change hotspot, where the frequency and intensity of summer temperature extremes are projected to increase. However, important uncertainties remain regarding the representation and predictability of heatwave-related atmospheric conditions at seasonal timescales.

This study investigates major Mediterranean heatwave events during the 1991–2010 period using high-resolution, dynamically downscaled hindcast simulations produced with the Weather Research and Forecasting (WRF) model, driven by ERA5 and CFSR reanalysis data. Heatwave conditions are identified using ETCCDI indices, e.g. TX95p and TX99p, enabling a consistent characterization of moderate and extreme temperature events in terms of intensity, duration, and spatial extent across the Mediterranean region.

The analysis focuses on a set of prominent historical heatwave episodes within the study period and examines their associated large-scale atmospheric conditions and regional circulation features. Particular attention is given to the ability of the simulations to reproduce the timing, spatial patterns, and persistence of these events, as well as the broader atmospheric environments in which they develop.

To evaluate model performance and predictability, all WRF-based simulations are analyzed at a common 3-month lead time, allowing for a uniform examination of their ability to reproduce heatwave-relevant circulation regimes and extreme temperature characteristics. This includes an evaluation of event representation, spatial patterns, persistence, and associated large-scale circulation features. The comparison provides insight into the capabilities and limitations of dynamical downscaling for representing Mediterranean heat extremes.

Overall, the study aims to improve the understanding of Mediterranean heatwave behavior and to evaluate the capability of regional dynamical downscaling systems and seasonal forecast models to represent and anticipate extreme summer temperature conditions.

Acknowledgements: This research was supported by the PREVENT project that has received funding from the EU Horizon Europe framework programme (grant no. 101081276) / Part of the results presented in this work have been produced using the Aristotle University of Thessaloniki (AUTh) High Performance Computing Infrastructure and Resources.

How to cite: Velikou, K., Manios, E. M., Papadopoulos Zachos, A., Tolika, K., and Anagnostopoulou, C.: Seasonal Predictability and Dynamical Representation of Mediterranean Heatwaves Using WRF Simulations, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-27, https://doi.org/10.5194/egusphere-plinius19-27, 2026.

Extreme precipitation is one of the most dangerous meteorological phenomena, causing significant harm to people, structures, and crops, as well as resulting in economic losses. Due to their resolution and configuration, Convection-Permitting Models (CPMs) offer the potential to reproduce convective extreme precipitation. However, CPM simulations require long runtimes and generate large amounts of data, consuming significant computer storage. Therefore, it is necessary to establish a link between extreme events in CPMs and their counterparts in global climate models (GCMs) and regional climate models (RCMs). Identifying this link would allow selective use of CPMs only for days when significant precipitation is expected, reducing the need to run climate simulations over extended periods and focusing on specific days.

Three methods were tested for detecting potential extreme precipitation events in CPMs using GCM data: a fixed precipitation threshold, linear regression, and logistic regression. Convective precipitation and calculated instability indices (Lifted Index, K Index, CAPE, wind shear, moist convergence and wind convergence) were used in the selected GCM, EC-Earth. The methods were trained using the outputs of the CPM HCLIM38-AROME over the Scandinavian domain in the historical period (1986–2005). This domain was chosen for training because of the availability of longer time series, and it was further divided into three smaller subdomains for improved method evaluation. Additionally, RCM simulations (HCLIM38-ALADIN) were used to enhance the detection of extreme events. The RCM bridges the gap in grid spacing between the GCM and the CPM. For validation, standard statistical methods were used, such as hit rate, Matthews correlation coefficient, and ROC score.

Initial results using a convective precipitation threshold in the GCM show relatively successful forecasting of extreme precipitation in the CPM, with a hit rate of 0.42. Calculating instability indices and introducing linear and logistic regression further improve the results, increasing the hit rate to 0.51. When moving to smaller subdomains within the same period, the performance of all methods decreases somewhat, but linear and logistic regression remain effective in predicting days with extreme precipitation (hit rate varies from 0.35 to 0.43).

The next step was to introduce the intermediate RCM as an additional filter. With this modification, the extreme precipitation prediction results reach a hit rate of 0.65.

Finally, the methods are validated over the same domain for the same models in the future period (2081–2100), as well as over the pan-Alpine domain, which includes parts of the Mediterranean and Croatia, in the period 1996–2005. The results indicate that by using linear regression and the RCM as a filter, extreme precipitation events can largely be detected already in the GCM, allowing selective inclusion of the CPM, which leads to savings in computational resources and time.

How to cite: Omazić, B., Oštrić, S., Karaula, L., and Belušić, D.: Detection of potential extreme precipitation events in convection-permitting climate simulations using statistical methods in global climate models, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-30, https://doi.org/10.5194/egusphere-plinius19-30, 2026.

Adverse convective weather (including large hail, heavy rainfall, downbursts and tornadoes) has been identified as one of the main research focuses due to its high impact on densely populated regions. Some recent examples in the western Mediterranean are: giant hail in Catalonia (2022 and 2023) and northern Italy (2024), floods in Valencia and the Ebro Delta (2020, 2021, 2023 and 2024), or the August 2022 derecho (Balearic Islands, Corsica and northern Italy). Furthermore, this impact seems to be increasing in some areas, such as the Mediterranean basin itself, for several reasons.

This analysis considers a continuous period of 12 years (2014-2025) of 6-minute radar data to provide insight into convective behaviour and trends in Catalonia (NE Iberian Peninsula). We investigated those pixels defined as convective: reflectivity at low levels between 25 and 75 dBZ and maximum reflectivity at any level between 45 and 75 dBZ. For each pixel, the surface and maximum reflectivity, the 45 dBZ echotop, the coordinates and the time (date plus time) were estimated. We evaluated, spatially, monthly and annually, the occurrence of these pixels, among other properties (recurrence, area, events, etc.). This presentation introduces the first results of our research: an increase in convective activity during the warmest season (from June to August), particularly in areas with high topography; only in some areas does convective activity decrease slightly; and an overall positive trend of all the variables studied throughout the period. These results are consistent with other studies indicating increased convection associated with changes in the freezing level or the amount of precipitable water at lower levels.

How to cite: Rigo, T., Marcos-Matamoros, R., and Llasat, M. C.: Deep analysis of convective trends in Catalonia, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-52, https://doi.org/10.5194/egusphere-plinius19-52, 2026.

Drought is a recurring phenomenon in the Mediterranean climate that characterizes the Iberian Peninsula, but its manifestations vary in duration, extent, and severity. Studying it using current instrumental meteorological records poses no difficulties, and techniques exist for its calculation and graphical and cartographic representation. However, to understand the patterns of this phenomenon in its most severe and least frequent manifestations, one must rely on historical documentary sources that allow drought impacts to be identified and analysed at daily temporal resolution over the last five centuries.

In this study, we used data from the AMARNA platform, which contains 12,012 cases or units of information distributed in 1,672 drought episodes from 1450 to 1950 for the whole of Spain. This information on droughts has been obtained from historical documentary sources containing records of liturgical rogation ceremonies for rain (“pro pluvia”). These ceremonies were commissioned by municipal authorities to address this adversity, which affected the development of agricultural crops.

Each case corresponds to a specific rain-praying ceremony that was held and recorded in the official records. All records available in AMARNA have been subjected to a series of filters to exclude sporadic or scattered information from the analysis, and to focus the analysis on the episodes of greatest relevance and information density. Having access to AMARNA data allows us to characterise the behaviour of major drought episodes during the Little Ice Age and to place them in the context of the instrumental period.

Using data on recorded cases from AMARNA, a methodology has been developed to classify drought episodes according to their duration, spatial extent, intensity and documentary evidence density. The proposed classification provides a framework for identifying and comparing the most significant drought episodes currently known in Spain between 1450 and 1950. It also offers new opportunities to investigate long-term drought variability, spatial patterns, and the occurrence of extreme events during the Little Ice Age and the transition to the modern climatic period.

Acknowledgements

The authors acknowledge the grants from FLOODMED (PID2024-157662OB-C22), funded by the Spanish Ministry of Science, Innovation and Universities (MICIU/AEI/10.13039/501100011033) and by ERDF/EU.

How to cite: Barriendos, J., Gil-Guirado, S., Pérez-Morales, A., Wimberly, F., Ummenhofer, C., Cuadrat, J. M., Jover, G., and Mariano, B.: Temporal evolution of drought in Spain over the last 500 years using historical documentary sources and instrumental records, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-68, https://doi.org/10.5194/egusphere-plinius19-68, 2026.

Extreme precipitation events are among the major hazards in the Mediterranean region, owing to their multiple impacts on natural and human systems. Their characterisation and physical understanding have been the focus of decades of research, particularly in the context of changes driven by global warming. These events are frequently associated with cut-off lows, which may also involve the advection of cold air at the surface. However, events producing concurrent extreme rainfall and snowfall within hydrological basins have received comparatively less attention.

In late December 1944, one such event caused severe impacts in the Segura River Basin, in southeastern Spain, generating both flooding and snowfall of extraordinary magnitude. Some observatories recorded precipitation totals reaching 220 mm over consecutive rainy days, while several villages became isolated by snow depths of up to one metre. The event resulted in fatalities and substantial socioeconomic impacts. This study aims to improve our understanding of cold–wet compound extreme events in the Mediterranean region by characterising this historical case study and assessing changes from 1941 to 2021 through the identification of circulation-analogue events. To this end, we combine newspaper sources, precipitation and temperature observations, and ERA5 reanalysis data. Beyond the analysed case study, the main results indicate changes in the surface impacts associated with these events over recent decades. Overall, no increase in event frequency is detected, nor is there a robust signal of changes in atmospheric dynamics. However, analogue events in the recent period produce more precipitation, with an average increase of 9.4 mm per event compared to earlier-period analogues, and are warmer on average, mainly due to an increase in minimum temperature of 1.1 °C per event. These results point to changes in the characteristics of cold–wet compound extreme events under recent climate conditions.

Overall, this study highlights how integrating historical event reconstruction with circulation-analogue methods improves the understanding of compound extremes in the Mediterranean region. The results also illustrate how global warming is altering the surface impacts of these events, with relevant implications for flood risk and water resource management.

How to cite: Halifa-Marín, A., Calvo-Sancho, C., Gil-Guallar, M., Royo-Aranda, A., Vela-Tambo, J., Adell-Michavila, M., Torres-Vázquez, M. A., Franquesa, M., Lemus-Canovas, M., Domínguez-Castro, F., Latorre, B., El Kenawy, A. M., Beguería, S., and Vicente-Serrano, S. M.: Insights into the December 1944 Extreme Cold–Wet Event in Southeastern Spain: Evidence of Change in Its Present-Day Analogues, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-101, https://doi.org/10.5194/egusphere-plinius19-101, 2026.

The North-Western Mediterranean region, which is a semi-enclosed sea surrounded by mountains, is prone to severe events. The region is notably known as a key spot for strong wind, like mistral and tramontane, channelled and accelerated in the surrounding valleys, that induces sometimes damaging sea states. Heavy precipitation events also often occur when a moist and rapid marine low-level flow converges and/or encounters mountainous area, triggering and feeding stationary deep convective systems that lead to very localized, large amounts of rainfall in only some hours (typically more than 100 mm in less than 24 hours), generating flash-floods. Furthermore, the region is more and more frequently affected by (marine) heatwaves that intensify with climate change and have major impacts on public health, agriculture/fishery and biodiversity. All these extreme events rely on air-sea interactions during their onset and lifecycle, with complex responses and feedbacks in terms of ocean as atmospheric circulation and processes.

To better represent the mesoscale air-sea environment and the exchanges in numerical modelling and weather prediction systems, fine horizontal resolution and coupling are crucial. The AROBASE system assembles kilometer-scale limited-area models of the atmosphere, the ocean, and waves. Since summer 2024, a first AROBASE forecast demonstrator is applied daily over the Metropolitan France region. It couples the AROME numerical weather prediction model at 1.3 km resolution and the NEMO ocean model with a 1/36° resolution. A second version was deployed in autumn 2025 and adds a new coupling to take into account the impacts of waves on the air-sea exchanges. This study will present some comparisons of the atmosphere-ocean(-waves) AROBASE forecast with the (uncoupled) AROME operational forecast during recent severe meteorological situations that affected the North-Western Mediterranean region.

How to cite: Lebeaupin Brossier, C., Beuvier, J., Bouin, M.-N., Dalphinet, A., and Nicolay, F.: High-resolution atmosphere-ocean coupling impact on North-Western Mediterranean severe event forecasts with the AROBASE prediction system, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-61, https://doi.org/10.5194/egusphere-plinius19-61, 2026.

For over two decades, the State Meteorological Agency of Spain (AEMET) has developed and operated Limited-Area Ensemble Prediction Systems (LAM-EPS) to quantify forecast uncertainty and provide reliable predictability guidance for short-range high-impact weather events. Currently, the operational AEMET-γSREPS functions as a convection-permitting, multi-model, and multi-boundary condition ensemble. Deploying operational domains over the Iberian Peninsula, the Canary Islands, and the Antarctic Peninsula, this system supplies forecasters with a comprehensive suite of probabilistic products to assess diverse atmospheric scenarios and support adverse weather warning mechanisms. This presentation reviews the institutional trajectory of LAM-EPS at AEMET and outlines future strategic directions. Key upcoming milestones include the transition toward a single-model HarmonEPS system incorporating Stochastically Perturbed Parameterizations (SPP), developed within the collaborative frameworks of ACCORD-EPS and UWC-South.

How to cite: Gómez-Navarro, J. J. and Callado-Pallarès, A.: LAM-EPS Systems at AEMET: Evolution, Current Capabilities, and Future Perspectives, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-81, https://doi.org/10.5194/egusphere-plinius19-81, 2026.

Reliable Numerical Weather Prediction (NWP) are of utmost importance to our daily life. In addition, they are of fundamental to help mitigation of severe and catastrophic weather events.

Atmospheric water vapor is a fundamental element of weather forecasting, nevertheless its accurate observation is difficult, mainly because of its high spatiotemporal variability. 

A reliable way to estimate water vapor is through Global Navigation Satellite Systems (GNSS) satellites, whose signals are received from ground-based stations and permit to calculate Zenith Total Delay (ZTD). ZTD can be easily related to Precipitable Water Vapor (PWV). 

The GNSS observation at the zenith uses delays from different directions to improve the estimate of the delay in the vertical direction, thus strengthening the solution. This process, however, reduces the number of observations available for each GNSS receiver. Anyway, the high quality of GNSS observations in the zenit direction has become a reference for other instruments and has been widely assimilated in NWP models worldwide.

Estimating the delay in different directions poses challenges for the convergence of the solution and for errors in the retrieved slant total delay (STD). Similarly, while the assimilation of the zenith delay for GNSS receivers is well-established, the assimilation of the delay in the inclined directions remains largely unexplored.

In this work, GNSS information along slant paths is assimilated into the Weather Research and Forecasting (WRF) model. Two approaches are shown: the first considers the assimilation of the delay along slant paths, the second the assimilation of precipitable water vapor along slant paths.

In the first approach, the assimilation of STD is done through the use of tropospheric gradients in the East and North directions. Gradients assimilation has been recently added in a version of the WRFA Data Assimilation (WRFDA) and presented in the paper of Thundathil et al. (2024). The same method was applied in Torcasio et al. (2026). 

An application of GNSS gradients assimilation over Italy is presented. The impact on the precipitation prediction of GNSS gradients assimilation both alone or in combination with GNSS-ZTD data assimilation is shown for a case study, comparing the results with a model configuration not assimilating GNSS data. Results show an improvement when GNSS data assimilation is applied: event intensity and location are better represented and false alarms are reduced. The configuration assimilating both GNSS-ZTD and gradients has the best performance. 

A second experiment considers PWV data assimilation along slant paths (PWVS). In this case, the STD signal is converted in precipitable water vapor and assimilated in WRF, increasing the number of observations in comparison to the assimilation of precipitable water vapor in the vertical direction. We consider an experiment of one month showing the problems involved in the assimilation of PWVS, its results, and its comparison with corresponding forecast without the assimilation of GNSS observations and with the assimilation of GNSS delay in the zenith direction.

References

Torcasio R.C. et al. (2026) https://doi.org/10.1007/s12210-025-01399-1

Thundathil R. et al. (2024) https://doi.org/10.5194/gmd-17-3599-2024 

How to cite: Torcasio, R. C. and Federico, S.: Assimilation of GNSS delays along slant paths into the WRF model: two experiments over Italy, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-96, https://doi.org/10.5194/egusphere-plinius19-96, 2026.

Tornadoes and waterspouts in the western Mediterranean and Iberian region are low-frequency but potentially damaging hazards, whose spatial occurrence remains difficult to characterize using fixed geographical or climatological regions. This limitation is especially relevant for risk-sensitive applications, where local exceedance probabilities and return-period estimates require physically meaningful regional occurrence rates.

This work presents an objective framework for the environmental regionalization and probabilistic hazard assessment of tornado and waterspout occurrence over peninsular Spain and the Balearic Islands. A unified and quality-controlled event catalogue was built by merging national (SINOBAS/AEMET) and European (ESWD/ESSL) severe weather records, yielding 1185 tornado and waterspout events for the period 1992–2025 after duplicate removal. For each event, pre-event atmospheric environments were characterized using ERA5-derived thermodynamic, kinematic, and composite instability parameters extracted around the event location and time.

To move beyond fixed a priori regions, event environments were spatially aggregated over a hexagonal grid of approximately 50 km and summarized through robust environmental signatures. Dimensionality reduction via principal component analysis, followed by Ward hierarchical clustering with spatial connectivity, identified three objective environmental regions. These clusters provide a physically based spatial partition of tornado-favourable environments and are evaluated against a priori subregional divisions using supervised machine learning classifiers.

Building on this regionalization, the study develops an occurrence, point-scale exceedance, and 50-km neighbourhood return-period framework for tornadoes. Regional tornado rates are estimated by intensity class and combined with Monte Carlo path-geometry simulations and internal wind-speed exceedance fractions. These were used to derive exceedance curves EP(v,T) and threshold-based hazard maps consistent with the observed spatial heterogeneity of tornadic environments.

Results show that the data-driven regions capture coherent environmental regimes — shear-dominated in the west and southwest, thermodynamically charged in the central-southeast, and weakly forced in the north and east — that are not fully reproduced by fixed geographical subdivisions. A key outcome is a decoupling between occurrence and severity: the regimes that produce most tornadoes are not those that dominate the high-end wind hazard, since the least active, thermodynamically charged regime concentrates the most intense events and controls exceedance at the highest thresholds. The proposed framework provides a reproducible basis for tornado hazard mapping in Spain and the Balearic Islands, with potential applications to civil protection, territorial planning, and the assessment of risk-sensitive infrastructures.

How to cite: Agurto Barragán, G., Aroba Páez, J., Gutiérrez Álvarez, I., and Gutiérrez de San Miguel Herrera, E.: A data-driven regionalization and point-scale exceedance framework for tornado and waterspout hazard assessment in peninsular Spain and the Balearic Islands, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-33, https://doi.org/10.5194/egusphere-plinius19-33, 2026.

Although the definition of medicanes has been recently provided (Miglietta et al., 2025), the characteristics of the most intense among these cyclones have yet to be determined. This latter subcategory of medicanes includes cyclones that, during their mature phase, are driven almost exclusively by air-sea interaction and are responsible for the greatest damage.

In this context, we analyze 17 medicanes using ERA5 reanalysis data to study the role of upper-tropospheric processes in cyclone development. Using back-trajectory analysis, we investigated the presence of dry intrusions in the early and mature phases of cyclones. We found that the standard definition of a dry intrusion, characterized by a descent of 400 hPa in 48 hours, is rarely met. In contrast, weaker and shallower descents associated with PV streamers are more common. Although dry intrusions can accelerate warm core formation by promoting convection, the final intensity of the warm core depends critically on diabatic processes near the cyclone's center, as exemplified by Ianos.

In fact, in Ianos only marginal descending flows occur before the main tropical phase, yet this cyclone develops the most intense warm core among the analyzed cyclones. This prompted us to examine Ianos in detail using a WRF model simulation with a 3 km grid spacing. This simulation highlights the dominant contribution of diabatic heating to the cyclone's intensification already in the early stages and suggests a secondary role for the baroclinic forcing, indicating a different pathway in the cyclone's evolution. However, in the mature phase, a weak upper-level PV streamer contributes to the rapid deepening of the cyclone.

How to cite: Miglietta, M. M., Nigro, D., Giovannini, L., Bordoni, S., and Dafis, S.:  Toward the identification of different subcategories of medicanes, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-91, https://doi.org/10.5194/egusphere-plinius19-91, 2026.

This study investigates Storm Samuel (Medicane JOLINA), a cyclone that developed over the central Mediterranean during March 2026 and subsequently affected North Africa and Libya. The system originated as a baroclinic cyclone in the lee of Tunisia, evolving through a warm-seclusion phase before acquiring tropical-like characteristics during the final stages of its life cycle. The event therefore provides an ideal framework for exploring the mechanisms governing the transition between extratropical and tropical-like structures in the Mediterranean environment. A hierarchy of numerical experiments is performed using the Weather Research and Forecasting (WRF) model at convection-permitting resolution. Simulations include configurations with and without spectral nudging, experiments using observed high-resolution SST fields and SST fields from which mesoscale anomalies have been removed, a suite of uniform SST perturbation experiments, and a pseudo-global-warming (PGW) simulation based on the ensemble-mean climate change signal derived from multiple future projections. An ocean mixed-layer parameterization is employed to account for air–sea coupling processes. The results indicate that cyclone genesis and propagation are primarily controlled by large-scale atmospheric forcing and regional orographic effects, while air–sea interactions exert a secondary influence on the storm trajectory. In contrast, SST structure plays a substantially larger role in modulating cyclone morphology, convective organisation and precipitation. Mesoscale SST anomalies favour enhanced diabatic activity and more organised convection, whereas their removal leads to a weaker and less coherent precipitation response. Sensitivity experiments further highlight a systematic thermodynamic response to SST changes, while the PGW simulation suggests an amplification of precipitation-producing processes under future climate conditions. Overall, the study highlights the hybrid nature of the event and emphasises how large-scale dynamics govern cyclone evolution, while mesoscale air–sea interactions critically modulate the intensity and hydrological impacts of Mediterranean tropical-like cyclones.

How to cite: Ricchi, A., Sancho-Calvo, C., Serafini, P., Nastasi, M., D'Amico, C., Avolio, E., Ferretti, R., and Miglietta, M. M.: On the Air Sea interaction and Future Climate Sensitivity of a Winter Tropical-Like Cyclone Jolina, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-128, https://doi.org/10.5194/egusphere-plinius19-128, 2026.

As global warming alters atmospheric circulation, the trajectories and intensities of weather systems are shifting, posing severe threats to highly exposed coastal communities. While much attention is given to the Mediterranean area, the adjacent regions of Macaronesia and Western Europe are increasingly vulnerable to cyclones coming from the Atlantic. This study diagnoses the long-term trends and large-scale causalities driving northward trajectories of African Easterly Waves (AEWs), the primary precursors to tropical cyclogenesis in Atlantic basin.

A long data of 84 years of ERA5 reanalysis (1940–2024) is analyzed and an objective tracking algorithm is applied, to isolate a subset of anomalous AEWs (A-AEWs) that deviate from their climatological westward path. To improve the physical understanding of the synoptic-scale atmospheric and oceanic environments that force this early recurvature, these events are compared against a 30-year dynamic climatology.

The analysis reveals that A-AEWs are steered northward by a distinct large-scale configuration. A poleward-displaced and significantly strengthened Azores High, coupled with an enhanced mid-latitude trough over the northeastern Atlantic, disrupts the standard steering flow in the tropical belt. Simultaneously, anomalously warm sea surface temperatures within the wave’s recurving region and substantial modifications in low-level moisture transport act as critical thermodynamic drivers, allowing the incursion of these systems into regions traditionally cooler and with a less favorable environment.

The identified synoptic and oceanic anomalies positively condition the presence of tropical systems in the historically weakly active northeastern Atlantic. By unravelling the causal mechanisms linking large-scale circulation anomalies and regional air-sea variability, this study highlights an increasingly recurrent weather threat and underscores the urgent need for improved monitoring and prediction of these synoptic precursors to protect vulnerable European coasts in a changing climate.

How to cite: Rodríguez Acosta, E. J., Gómez Plasencia, P., González Alemán, J. J., Calvo Sancho, C., Díaz Fernández, J., Bolgiani, P., Luna Rico, M. Y., Montoro Mendoza, A., Martín Pérez, M. L., and Gómara Cardaalliaguet, I.: Synoptic Environments of Northward-Recurving African Easterly Waves: An Emerging Threat for Southwestern Europe, 19th Plinius Conference on Mediterranean Risks, Murcia, Spain, 6–9 Oct 2026, Plinius19-59, https://doi.org/10.5194/egusphere-plinius19-59, 2026.