Session 7 | Floods, flash floods, and convective storms within extratropical, tropical and hybrid cyclones

Session 7

Floods, flash floods, and convective storms within extratropical, tropical and hybrid cyclones

Orals TH2

| Thu, 20 Nov, 11:30–13:15 (CET)|Room Hertz Zaal

Posters TH4

| Attendance Thu, 20 Nov, 14:30–16:00 (CET) | Display Wed, 19 Nov, 09:00–Thu, 20 Nov, 18:30|Poster area, P29–39

Orals: Thu, 20 Nov, 11:30–13:15 | Room Hertz Zaal

11:30–11:45

ECSS2025-57

A phenomenological definition of "medicane"

Mario Marcello Miglietta and the medicane definition group

Vortices with visual characteristics typical of tropical cyclones, such as cloudless eye-like features surrounded by spiraling clouds and rainbands, are occasionally observed in the Mediterranean. These systems form a peculiar subcategory of Mediterranean cyclones, known in the scientific literature as medicanes (a portmanteau of the words “Mediterranean hurricanes”). Despite their limited number (about 1-3 events per year), medicanes are directly related with high impact weather (e.g., strong wind gusts, high sea waves, and heavy precipitation) and thus have been constantly attracting the interests of both the scientific community and the general public.

Unfortunately, the term “Mediterranean tropical cyclone” or “medicane” has been used in different ways by different authors. Some definitions are based on visual features detected in satellite imagery, others on structural characteristics derived by diagnostics applied to numerical weather prediction outputs. The absence of an official or commonly accepted definition has created some confusion within the scientific and weather forecaster community. Moreover, recent case studies on the dynamics of several systems widely recognized as medicanes show different underlying development mechanisms.

Following the outcomes of two recent projects (“MedCyclones”, supported by COST–European Cooperation in Science and Technology, and “MEDICANES”, supported by the European Space Agency), a phenomenological definition of “medicane” was proposed, which is based solely upon earth observations and accommodates the cases analyzed so far in previous studies. This commonly agreed definition is necessary to assess their climatology in past and future climate, as well as to objectively identify such systems in weather forecasts.

How to cite: Miglietta, M. M. and the medicane definition group: A phenomenological definition of "medicane", 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-57, https://doi.org/10.5194/ecss2025-57, 2025.

Discussion Post a comment

11:45–12:00

ECSS2025-249

Evaluation of extreme precipitation events across different timescales: A comparison of high-resolution modeling and observed data in Emilia-Romagna

(withdrawn)

Oliver Carlo, Giusy Fedele, Silvio Gualdi, Paola Mercogliano, and Piero Lionello

12:00–12:15

ECSS2025-22

Flash floods in Croatia from 2012 till 2022 – meteorological analysis

Klara Severić, Tanja Renko, Maja Telišman Prtenjak, and Vinko Šoljan

Flash flood forecasting and warnings remain highly challenging for many national meteorological and hydrological centers. In recent years, significant advancements have been made in hydrological and meteorological modeling, leading to rapid progress in forecasting capabilities. However, flash floods continue to cause substantial material damage and claim lives worldwide.

The purpose of this study is to gain a better understanding of the parameters and meteorological conditions necessary for flash flood events in various parts of Croatia, with the goal of improving prediction accuracy. Additionally, the authors emphasize that maintaining comprehensive databases of extreme events is essential for the further development of prognostic tools and warning systems. Recent studies also highlight the intensification of short-term precipitation, which, when combined with topographical features that favor heavy rainfall, underscores the importance of studying such events to mitigate the effects of climate change.

An ingredient-based methodology introduced in the 1990s suggests that the favorable combination of these ingredients can be identified across a wide range of synoptic and mesoscale situations. Therefore, it is crucial to analyze how these ingredients interact with Croatia's unique climate and orography. The use of a so-called flash flood checklist, integrating both meteorological and hydrological factors, can aid operational workflows and decision-making processes within national meteorological and hydrological services (NMHSs).

For the analysis of flash floods in the Republic of Croatia, 97 events from the period 2012 to 2022 were examined. A majority of the cases, 66 events (68% of the total), occurred in the coastal regions of Croatia. As expected, the largest number of events was recorded during the warm part of the year, with September standing out due to significant contributions from events in coastal areas, followed by June. Synoptic conditions were also analyzed, identifying two dominant weather types: the leading side of a trough with pronounced southwesterly flow and cut-off low. Thermodynamic conditions for 87 cases were assessed using upper-air sounding data, and a wide range of parameters and indices were analyzed and discussed.

How to cite: Severić, K., Renko, T., Telišman Prtenjak, M., and Šoljan, V.: Flash floods in Croatia from 2012 till 2022 – meteorological analysis, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-22, https://doi.org/10.5194/ecss2025-22, 2025.

Discussion Post a comment

12:15–12:30

ECSS2025-181

Exploring extreme floods in two Italian watersheds through unseen ensemble scenarios

Agostino Manzato, Elena Bianco, Giuseppe Zappa, Paolo Davini, and Paolo Ruggieri

Panàro and Reno are two rivers in N-Italy having adjacent mid-sized watersheds. Given their spatial proximity they are expected to respond similarly to meteorological forcing leading to extreme floods. Three different river discharge (RD) datasets are analyzed: 1) the historical daily-mean observed timeseries by ARPAE in the stations of Bomporto (Panàro) and Casalecchio (Reno); 2) the EFAS5 historical simulations of daily-mean, computed using the LISFLOOD hydrological model forced with the EMO1 dataset (1992-2023); and 3) the EFAS seasonal-reforecast daily-mean, computed by LISFLOOD forced by the 25-member SEAS5 ensemble (2000-2023).

The UNSEEN approach (UNprecedented Simulated Extremes using ENsembles) uses many simulations to identify “plausible” extremes. Building upon this approach, an ensemble of 100 “surrogate” timeseries is built by concatenating 4-month-blocks from the original 25-EFAS members, skipping the first 3-months of each timeseries to ensure statistical independence. This is done starting from four different initial dates (beginning of April, May, June, and July). RD in two stations are compared by inspecting quantiles, interannual trends, and annual cycles. It is found that the 100 surrogate timeseries in Bomporto can produce RD-extremes higher than those seen in the historical EFAS dataset. The surrogate timeseries show a mostly bell-shaped distribution, centered around zero, for the slope of the interannual trend, while both the historical EFAS timeseries and the ARPAE observations show a positive trend, in recent years. With respect to the annual cycle, autumnal extremes appear to be strongly underestimated in the surrogate timeseries (particularly at Casalecchio), due to an underestimation of the local precipitation from September to December.

Possible relations with RD are explored by examining the meteorological synoptic conditions associated with the most extreme floods, in both the historical-ERA5 and in the surrogate-SEAS5 worlds. The meteorological conditions leading to floods in Bomporto and Casalecchio (only 33 km apart) seem different: the most extreme events at Bomporto are typically associated with deep trough over the Mediterranean or a cyclone over Central-Italy, while those at Casalecchio seem to be linked to a less meridional flow and deeper Atlantic depressions. The frequency of synoptic configurations associated with RD-extremes is studied in both the historical and surrogate worlds, to assess whether the surrogate simulations reveal unseen patterns, or a higher frequency of extreme-RD configurations. Lastly, Z500 and MSLP are used together with local precipitation, to develop a CNN-based statistical model able to characterize the RD-extremes and compare performances on historical and surrogate worlds.

How to cite: Manzato, A., Bianco, E., Zappa, G., Davini, P., and Ruggieri, P.: Exploring extreme floods in two Italian watersheds through unseen ensemble scenarios, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-181, https://doi.org/10.5194/ecss2025-181, 2025.

Discussion Post a comment

12:30–12:45

ECSS2025-147

Flood map interpolation from design storms under global warming using a national hydrodynamic model database in Aotearoa New Zealand

Joe Pelmard, Alice Harang, Cyprien Bosserelle, Emily Lane, Trevor Carey-Smith, Rose Pearson, Conrad Zorn, Luisa Hosse, and Ryan Paulik

Severe storms are among Aotearoa New Zealand’s costliest natural hazards, with escalating impacts under climate change due to both direct flood damage and cascading disruptions to infrastructure and supply chains. As part of a national flood risk assessment framework, we present a methodology for the rapid estimation of flood hazard maps corresponding to storm-driven rainfall events under current and future climate conditions.

The approach leverages NIWA’s national database of hydrodynamic flood model outputs (280+ domains, 64–8 m adaptive resolution) which simulate design storms with annual recurrence intervals (ARIs) from 10 to 1000 years under current conditions. Multiple regression techniques are evaluated for interpolating flood maps at unmodelled ARIs. Polynomial regression consistently yields better fits and is used to generate a library of gridded regression coefficients that enables rapid flood extent estimation across domains.

To account for global warming (ΔT), current rainfall intensities are converted to temperature-adjusted ARI maps using both an iterative solver and a log-cubic regression, with comparable accuracy. Considering the spatial variability of the mapped ARI in some domains, relevant aggregation methods are discussed to compute a single representative ARI_D_T estimates for each modelled domain. For ΔT=+1°C and +3°C, the available flood depth and extents show appreciable agreement with hydrodynamic output modelled for [ARIΔT, ΔT]-based design storms in domains with high ARI_D_T dispersion.

Rather than bypassing full hydrodynamic modelling, these combined approaches allow computational resources to be focused on simulating the most severe design storm conditions (ARI>200y). This offers a scalable framework to prioritize the enhancement of the national flood hazard mapping database under evolving climate conditions. The database will later be extended to incorporate sea-level rise, enabling a matrix of future flood risk scenarios.

How to cite: Pelmard, J., Harang, A., Bosserelle, C., Lane, E., Carey-Smith, T., Pearson, R., Zorn, C., Hosse, L., and Paulik, R.: Flood map interpolation from design storms under global warming using a national hydrodynamic model database in Aotearoa New Zealand, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-147, https://doi.org/10.5194/ecss2025-147, 2025.

Discussion Post a comment

12:45–13:00

ECSS2025-111

A multi-scale analysis of atmospheric processes associated with dam overtopping events in the Eastern United States

Deanna Hence, Jacqueline Sepulveda, and Hodo Orok

This study uses WRF high-resolution numerical modeling case analysis and catchment-level statistical characterization of reanalysis and precipitation datasets to examine the evolution atmospheric conditions associated with hydrologic dam incidents in the eastern United States. Extreme precipitation elevates the risk of dam overtopping, which is the main cause of a third of US dam failures. As the intensity of precipitation is predicted to increase in future climates, understanding the evolution of precipitation-generating features within the atmospheric system, alongside the hydrologic response leading up to the failure, is a crucial initial step in properly characterizing and predicting the risk of dam failures during a range of weather events.

Case study analysis reveals that the Appalachian Mountains have the potential to play a role in these events, even at distance from the terrain itself, owing to complex interactions between orographically-blocked flows, fronts, and other meteorological phenomena like tropical cyclones. Statistical analysis of four subregions of the US eastern seaboard 30-days period prior to a dam’s hydrologic incident further highlight that combinations of these phenomena present more risk for high numbers of failures than each phenomenon alone. Ongoing analysis of the sub-regions seeks to characterize variations across the region, identify the role of persistent atmospheric patterns, and provide deeper insight into processes that determine how precipitation is distributed within the catchment.

How to cite: Hence, D., Sepulveda, J., and Orok, H.: A multi-scale analysis of atmospheric processes associated with dam overtopping events in the Eastern United States, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-111, https://doi.org/10.5194/ecss2025-111, 2025.

13:00–13:15

ECSS2025-85

The Northern Mesonet Project: Creation of an interconnected network of surface weather station networks in Canada

Connell Miller, Collin Town, Minh Nguyen, and Josh Muszka

Surface weather stations are a critical technology for understanding severe convective storms due to their unique capabilities. While weather radar effectively detects precipitation and wind patterns aloft, its limitation is its inability to capture crucial surface-level weather where it matters the most for people and property. Documenting and analyzing such events offer invaluable insights into their causes, impacts, and potential future occurrences.

Existing surface weather stations in Canada frequently face several known limitations that impede their effectiveness, especially when it comes to severe convective storms. In general, Canadian surface weather stations are widely spaced which often fail to capture highly localized severe convective storms. Additionally, the operation of these stations is managed by different federal and provincial agencies, which makes it difficult to utilize existing surface weather stations for nowcasting severe convective storms. Furthermore, it poses challenges in collecting data after an event, as the ease of access to this data can vary greatly across these different agencies.

This is the reason for the creation of Northern Mesonet Project (NMP), a new program under the Canadian Severe Storms Laboratory, which aims to better monitor severe convective storms by increasing the spatial density of real-time advanced weather observations and enhancing data availability & quality for severe weather analysis and prediction. This presentation will specifically highlight the Canadian Mesonet Portal, a central repository and access point established by NMP to address some of the limitations faced by Canadian surface weather stations. By connecting over 30 individual surface weather station networks, the Canadian Mesonet Portal provides a unified platform for accessing over 2800 publicly available surface weather observations across Canada. This unified platform allows for better nowcasting of severe convective storms in Canada, and for better analysis of the damage caused by severe convective storms.

How to cite: Miller, C., Town, C., Nguyen, M., and Muszka, J.: The Northern Mesonet Project: Creation of an interconnected network of surface weather station networks in Canada, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-85, https://doi.org/10.5194/ecss2025-85, 2025.

Posters: Thu, 20 Nov, 14:30–16:00 | Poster area

Display time: Wed, 19 Nov, 09:00–Thu, 20 Nov, 18:30

P29

ECSS2025-78

Identification of distinct types of surface-water-flood-producing convection in the UK

Matthew Clark and Andrew McNaughton

A set of 103 cases of convection resulting in substantial surface-water flooding (SWF) impacts in the UK between 2015 and 2021 has been constructed. The morphologies and environments of these storms have been explored using observations, model data, and ERA5 proximity soundings. Most SWF-producing storms were found to comprise multicellular systems; however, these exhibited a very wide range of morphologies and spatial scales across the event set. Whilst the environments of these storms were typically characterised by rather small CAPE and weak vertical wind shear (median CAPE of ~560 J kg^-1 and median effective bulk wind difference of ~13 knots), a wide range of environmental conditions was noted, ranging from cases with meagre CAPE, low equilibrium levels and strong boundary layer convergence (e.g., along well-marked surface fronts) to cases with large CAPE and high equilibrium levels. Cases also ranged from those with very strong flow in the boundary layer and/or the convective layer as a whole, to those with very weak flow in these layers. Furthermore, examples of both elevated and surface-based convection are represented within the event set.

Faced with this variability, we have employed clustering analysis to objectively define different types of SWF-producing storms in the UK. In this presentation, we will outline the clustering methodology and describe the key characteristics of the several identified event types. A longer-term goal is to understand whether storm environmental characteristics, morphologies and/or physical processes (e.g., those potentially having a bearing on the likelihood and/or location of triggering of secondary cells) vary systematically between types; if so, this information could potentially be used to alert forecasters to mechanisms that are likely to be most relevant on any given day that SWF impacts are possible (alternatively, it may be that there are no clear systematic differences in these respects between types, e.g., if such processes depend on storm-scale factors that cannot be represented in the proximity sounding data or be resolved by available observations). We also seek to explore how the performance of two recently developed observations-based nowcasting tools (the PLUVIA mesoanalysis and PLUVIA cell tracker) varies between types, in order to provide more nuanced guidance to Operational Meteorologists in their use of these new tools.

How to cite: Clark, M. and McNaughton, A.: Identification of distinct types of surface-water-flood-producing convection in the UK, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-78, https://doi.org/10.5194/ecss2025-78, 2025.

Discussion Post a comment

P30

ECSS2025-89

Analysis of Extratropical Cyclone Circulation Centroids using Ultra-High-Resolution 3D Radar Wind Fields in the Seoul Metropolitan Area

So-Yeon Park, Bo-Young Ye, and Mi-Kyung Suk

Extratropical cyclones, meso- to synoptic-scale atmospheric vortices, are characterized by rising, converging air masses, are associated with low-pressure systems and frontal boundaries, frequently causing substantial damage through intense winds and heavy precipitation. Traditional monitoring approaches utilizing radar reflectivity encounter significant limitations when addressing spatial shifting or regional variations in precipitation. To overcome these challenges, we propose a novel technique for tracking extratropical cyclones through the detection of cyclonic circulation centroid from radar wind fields using a multi-parameter analysis.
This method employs high-resolution 3D wind data from the Korea Meteorological Administration's radar network, processed through the “WInd Synthesis System using Doppler Measurements (WISSDOM)”, which provides comprehensive wind data across multiple altitudes, facilitating 3D characterization of precipitation system dynamics (Liou et al. 2012, Kim et al. 2018). We objectively identify cyclonic rotation centers by analyzing wind direction, speed, and vorticity from WISSDOM. When applied to 50 extratropical cyclone cases during 2023-2024, this technique successfully detected centers in 46 cases (92% success rate) (Park et al. 2025).
In this study, we applied this advanced technique to the Seoul Metropolitan area using ultra-high-resolution radar wind fields specifically designed for densely populated urban environments. We generated these enhanced wind fields by improving the spatial resolution of WISSDOM wind data. Our three-step approach includes: 1) identification of potential cyclonic centers based on wind velocity and vorticity analysis, 2) examination of cyclonic vorticity areas through wind direction patterns analysis, and 3) determination of the optimal cyclonic center location. The analysis of vertical structure within these systems through our method enables the identification of developmental stages and intensity variations, as well as the temporal tracking of cyclone movement trajectories. This research substantially advanced our understanding and predictive capabilities for extratropical cyclones and associated severe weather phenomena. The technique also demonstrated significant potential for extension to tropical cyclone and mesocyclone centroids detection, facilitating enhanced early warning system for torrential rainfall events.

Acknowledgements:
This research was supported by “Development of radar based severe weather monitoring technology (KMA2021-03121)” of “Development of integrated application technology for Korea weather radar” project funded by the Weather Radar Center, Korea Meteorological Administration.

Keywords:
Cyclonic Circulation, Extratropical Cyclone, 3D Doppler radar wind field, WISSDOM, Weather Radar Network

How to cite: Park, S.-Y., Ye, B.-Y., and Suk, M.-K.: Analysis of Extratropical Cyclone Circulation Centroids using Ultra-High-Resolution 3D Radar Wind Fields in the Seoul Metropolitan Area, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-89, https://doi.org/10.5194/ecss2025-89, 2025.

P31

ECSS2025-119

Using satellite data to examine the oceanographic processes over warm and cold core eddies in Bay of Bengal

Humberto Barbosa

The Bay of Bengal is home to a significant number of tropical cyclones. Tropical cyclones have been the major attention to the meteorological communities due to their varied socio-economic impacts. Recent studies have shown that tropical cyclones can feedback to the large-scale air-sea interactions. Since the Bay of Bengal is a part of the Indo-Pacific warm-pool region, small changes in the thermal structure of the Bay could alter the air-sea interactions. Because the Bay of Bengal is part of the Indo-Pacific warm pool zone, it is vulnerable to large-scale distant forcing from El Niño Southern Oscillation (ENSO) and other natural disasters. This study particularly deals with the impact of tropical cyclones (pre and post-monsoon seasons) on the Bay of Bengal. The role of mesoscale eddies in the intensity and movement of tropical cyclones has been studied in detail as case studies. Different satellite-based oceanographic observations are used in the analysis. The study concludes that distinct ocean processes have a relative role in impacting mixed layer temperature. It is examined distinct physical oceanographic parameters and conducted a thorough oceanic mixed layer heat budget analysis. Among which, for the warm case of warm-core eddies, pre-existing barrier layer plays a crucial role in impacting the mixed layer temperature.

How to cite: Barbosa, H.: Using satellite data to examine the oceanographic processes over warm and cold core eddies in Bay of Bengal , 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-119, https://doi.org/10.5194/ecss2025-119, 2025.

P32

ECSS2025-175

A comparative study of observational and reanalysis data for extreme precipitation events in the Spanish Mediterranean

Jesús Gutiérrez-Fernández, Carlos Correa, Irene Rodriguez-Muñoz, María Ortega, Alfonso Hernanz, Juan Jesús Gonzalez-Alemán, and Esteban Rodríguez-Guisado

Extreme precipitation events in the coastal regions of the Spanish Mediterranean represent a significant meteorological risk due to their potential to cause flooding and other socio-economic impacts (Mateos et al., 2023). These extreme events are commonly associated with the autumn months, when atmospheric instability increases following the summer season, and Mediterranean Sea temperatures remain relatively high (Nieto-Ferreira, 2021). The interaction between the warm, moist air from the sea and the descending cold air aloft favours the formation of intense convective systems, leading to episodes of extreme rainfall (Mastrantonas et al., 2020). From a climatological perspective, the capacity of climate reanalysis data tends to underestimate extreme precipitation values.

Therefore, the main motivation of this work is to perform a comparative study between the hourly observational data from AEMET and different high-resolution reanalyses: CERRA (Schimanke et al., 2021), CERRA-Land (Verrelle et al., 2022), EOBS (Cornes et al., 2018), ERA5-Land (Muñoz-Sabater et al., 2024) and ERA5 (Hersbach et al., 2023). This study focus on the Mediterranean basin regions of Spain, covering the period from 1995 to 2022 during the autumn months.

The aim of this work is to assess the reliability of these reanalysis data in representing the most extreme precipitation events and to determine whether current reanalysis data can adequately capture the intensity, frequency, and spatial distribution of these events, which is crucial for improving predictions and management strategies for severe weather phenomena.

How to cite: Gutiérrez-Fernández, J., Correa, C., Rodriguez-Muñoz, I., Ortega, M., Hernanz, A., Gonzalez-Alemán, J. J., and Rodríguez-Guisado, E.: A comparative study of observational and reanalysis data for extreme precipitation events in the Spanish Mediterranean, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-175, https://doi.org/10.5194/ecss2025-175, 2025.

P33

ECSS2025-178

Investigating the development conditions for cyclones with tropical features in the Mediterranean Basin.

Jesús Gutiérrez-Fernández, Carmen Alvarez-Castro, Juan Jesús González-Alemán, and Esteban Rodriguez-Guisado

In recent years, the impact of cyclones with tropical characteristics in areas of the Mediterranean
Sea, also called Medicanes (MEDIterranean hurriCANES; Emanuel, 2005), has caused extensive
damage, particularly in coastal areas of Greece, Italy and North Africa. These cyclones have a
relatively low frequency in Mediterranean areas, although they are associated with extreme
weather phenomena (heavy rainfall, strong winds, and landslides). Therefore, the main goal of this
work is to create an index of meteorological conditions that can determine favourable
environment for the development of cyclones with tropical characteristics in the Mediterranean
basin. For this purpose, we have selected some of the most intense Medicanes occurring during
the last years. Using ERA5 data we study variables such as Convective available potential energy
(CAPE), coupling index (CI; Bosart & Lackmann, 1995), Wind shear, Geopotential in 500 hPa and
Sea surface temperature (SST).The findings of this study reveal that the development of cyclones
with tropical characteristics in the Mediterranean is strongly linked to the formation of an intense
trough, which is exposed to strong convective processes (high CAPE and CI values), low wind shear
at high levels and a Mediterranean Sea temperature above 15oC. The combination of all these
conditions at the same time is quite uncommon, so this could explain the infrequent and extreme
nature of this type of cyclones.

How to cite: Gutiérrez-Fernández, J., Alvarez-Castro, C., González-Alemán, J. J., and Rodriguez-Guisado, E.: Investigating the development conditions for cyclones with tropical features in the Mediterranean Basin., 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-178, https://doi.org/10.5194/ecss2025-178, 2025.

P34

ECSS2025-193

Dynamic tropopause folding and cyclogenesis in the western Black Sea basin

Meda Daniela Andrei

For Romania, May 2025 stood out for numerous severe and extreme phenomena (abundant amounts of water, medium and large hail, strong wind). Under these conditions, this month rose to 4^th place in the ranking of the rainiest months since measurements were taken. There have been several episodes of heavy rain, but the last one, from June 23 to 30, affected the eastern half of Romania and even caused an ecological disaster at the Praid salt mine located in the central-eastern part of Romania (eastern Transylvania). It was flooded and collapsed mainly due to the rise of the Corund River, whose flow was almost 100 times higher than normal. For this study, the days of May 26 and 27 were chosen because the synoptic and mesoscale context was special, and caused heavy rains. It is about a cyclone that developed over the western Black Sea basin, with the main factor being the folding of the dynamic tropopause. When a potential vorticity anomaly overlaps a baroclinicity zone it makes possible dynamically and thermodynamically interactions between the lower and the upper troposphere. The western Black Sea basin, especially the coastal area, may provide the necessary conditions for such coupling leading to severe cyclogenesis. Under these conditions, very active cyclones are generated over the Black Sea, which when they are close to the shore, cause heavy rains and/or strong winds in the eastern half of Romania. Thus, the aim of this paper is to demonstrate the importance of dynamic tropopause fold in the development of a cyclone over the west part of the Black Sea basin and how strong can affect Romania, even with natural disasters. For the study, ALARO (ALadin-AROme) limited area spectral model analyzes and ECMWF global model analyes (eg, mean sea level pressure, geopotential high at 500hPa, 1,5 PVU field height, 300 hPa Potential Vorticity, 300 hPa winds,), data from meteorological stations, cross-sections and satellite images were used. The results of this study is important because can be used in operational forecast, for similar situations, and can improve it.

Keywords: ecological disaster, tropopause fold, cyclogenesis, havy rain

How to cite: Andrei, M. D.: Dynamic tropopause folding and cyclogenesis in the western Black Sea basin, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-193, https://doi.org/10.5194/ecss2025-193, 2025.

P35

ECSS2025-201

The role of Mediterranean cyclone structure in modulating convective activity

Olivia Martius, Alice Portal, Andrea Angelidou, Raphael Rousseau-Rizzi, Shira Raveh-Rubin, Jennifer Catto, Francesco Battaglioli, Jonatan Givon, Emmanouil Flaounas, and Mateusz Taszarek

Deep convection in the Mediterranean is favoured by warm sea surface temperatures and complex topography, but its occurrence is further modulated by synoptic-scale systems such as Mediterranean cyclones (MEDCs). In this study we investigate how MEDCs influence the frequency and intensity of convective environments and associated hazards. The analysis combines ERA5 reanalysis data, modelled hail and lightning probabilities, and lightning detections from the ATDNet network. A recent classification of MEDCs into nine clusters based on upper-level dynamical structure (Givon et al., 2024) provides a framework for linking cyclone types to convective activity.

For each MEDC cluster, we examine the evolution of convective environments, highlighting key differences in their spatial distribution and timing relative to the cyclone centre. In general, convective activity is most frequent northeast of the cyclone centre and within the warm sector, typically peaking before the time when the minimum central pressure is reached. Among the clusters, small and deep cyclones in the northern Mediterranean during autumn show the highest potential for severe convection, followed by weaker systems occurring in the southern Mediterranean during autumn, spring and summer.

We further identify mesoscale features within MEDCs and show that regions of warm conveyor belt ascent are more strongly linked to deep convection than cold frontal zones. This pattern is consistent across all cyclone types. Our findings advance the understanding of convective processes associated with MEDCs and offer valuable insights for improving weather forecasting and risk communication in the Mediterranean region.

Givon, Y., Hess, O., Flaounas, E., Catto, J. L., Sprenger, M., and Raveh-Rubin, S.: Process-based classification of Mediterranean cyclones using potential vorticity, Weather Clim. Dynam., 5, 133–162, https://doi.org/10.5194/wcd-5-133-2024, 2024.

How to cite: Martius, O., Portal, A., Angelidou, A., Rousseau-Rizzi, R., Raveh-Rubin, S., Catto, J., Battaglioli, F., Givon, J., Flaounas, E., and Taszarek, M.: The role of Mediterranean cyclone structure in modulating convective activity, 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-201, https://doi.org/10.5194/ecss2025-201, 2025.

P36

ECSS2025-202

Convective activity behaviour on tropical cyclones impacting Europe in a warmer world

Juan Jesús González-Alemán, Pedro Gómez-Plasencia, Carlos Calvo-Sancho, Íñigo Gómara, and Maria Luisa Martín-Pérez

Tropical transition (TT) events represent a complex interaction between baroclinic and tropical processes in cyclones, often leading to high-impact tropical cyclones in the mid-latitudes. The cyclones start as extratropical cyclones and then surface enthalpy fluxes and convective activity are able to transform the structure of the cyclone. As the climate warms, changes in atmospheric thermodynamics may alter the structure and convective behavior of these special systems.

In this work, we analyze how convective activity evolves during the TT of cyclones in a warmer climate context. Using high-resolution meteorological simulations with the HARMONIE-AROME model, operational at AEMET, from both historical and future climate conditions, we examine an archetypal TT case (Tropical Storm Delta, 2005) in the North Atlantic, which led an extraordinary impact in the Canary Islands (Spain). We perform the pseudo-global technique and analyze convective activity using the cloud tracking TOBAC. Particular attention is paid to behavior, organization, intensity, and spatial distribution of convection during the transition phase and how it then alters cyclone dynamics. We also assess how warming-related factors affect convective development. Our results aim to improve the conceptual understanding of TTs under climate change and open a line of support for adapting future forecasting strategies for these potentially hazardous system.

How to cite: González-Alemán, J. J., Gómez-Plasencia, P., Calvo-Sancho, C., Gómara, Í., and Martín-Pérez, M. L.: Convective activity behaviour on tropical cyclones impacting Europe in a warmer world , 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-202, https://doi.org/10.5194/ecss2025-202, 2025.

P37

ECSS2025-252

Influence of embedded convection on precipitation amounts.

Martin Adamovský, Miroslav Šinger, Marie Glofáková, and Filip Smola

Subject of this poster is to closely examine the influence of an embedded convection during the severe floods in September 2024. During this high impact situation, several bands of convection affected areas in eastern parts of Czechia and western regions of Slovakia and enhanced the precipitation amounts significantly. The combination of convective precipitation and upwind effect caused a numerous absolute precipitation records in both countries. For example in Slovakia, a new record was set for 48 hours (267,3 mm - Borinka weather station) and 5 days (379,8 mm - Pernek weather station) total precipitation. In Czechia, 385,6 mm was measured at Švýcárna automatic weather station and marked this number like a new absolute 24 hours record.

Wider forecaster perspective in these situations is focused mainly on orographic effects of precipitation in complex orography which enhance the overall sums of rainfall. This phenomena is well known for forecasters and the skill of high resolution numerical models to simulate these effects is usually quite acceptable. On smaller scale however, embedded convection can also play significant role in overall contribution of precipitation amount and precise forecast of these very local bands of higher precipitation amounts is very challenging. We tried to compare the regions, where upwind effect was mainly responsible for the highest precipitation and regions where this effect was boosted with the presence of embedded convection. We examine other similar situations from the past as well, floods in 1997, 2010, 2018, etc.

How to cite: Adamovský, M., Šinger, M., Glofáková, M., and Smola, F.: Influence of embedded convection on precipitation amounts., 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-252, https://doi.org/10.5194/ecss2025-252, 2025.

P38

ECSS2025-259

Characterization of thunderstorms to detect, track and extrapolate supercells.

Moureaux Mathilde, Bouilloud Ludovic, Lepy Olivier, and Le Bastard Tony

Supercells represent a major safety issue due to violent phenomena they can provoke, such as large hail, severe wind gust, heavy rain and, sometimes, tornadoes.That’s why this issue has been taken head-on and a dedicated product for purposes of detection, tracking and nowcasting of supercells was developed.

For this implementation and evaluation of the algorithm, an extensive study of severe thunderstorms and, in particular, supercells, has been performed. A national database of severe convection events (multicell, supercell, isolated cell), their location and evolution in time, is first created from the ESWD database.

This national database is then further improved by two existing products at Météo France:

(i)- Detection of mesocyclones using the French radar network. Radial velocity field from Doppler radars is used as criteria to identify the presence of mesocyclones. This technique is based on work by Zrnic et al. (1985), largely inspired by Hengstebeck et al. (2018) and presented at ERAD 2022 by Tony Le Bastard.

(ii)- Object for convection nowcasting (a.k.a. OPIC), developed by Bernard-Bouissieres I. at DIROP/PI (*). It is an operational product based on reflectivity field and the satellite observations of lightnings. It provides various information about geometry, reflectivity, direction and speed of movement, lightning and other…

As a result, the upgrade version of the database includes the spatial properties of storm cells: altitude, geometry, reflectivity and precipitation, direction and speed movement, lightning, mesocyclones, shear as well as the evolution of these parameters during the lifetime of thunderstorms.

The OPICs are used for the detection, tracking and nowcasting of convective cells. Mesocyclone detection and the application of certain criteria extracted from a database study make it possible to identify supercells among other cell types.

The preliminary results as well as the product limitation and advantages will be presented.

*. dirop_pi@meteo.fr

Zrnić, D. S., Burgess, D. W., & Hennington, L. D. (1985). Automatic detection of mesocyclonic shear with Doppler radar. Journal of Atmospheric and Oceanic Technology, 2(4), 425-438, https://doi.org/ 10.1175/1520-0426(1985)002,0425:ADOMSW.2.0.CO;2

Hengstebeck, T., Wapler, K., Heizenreder, D., & Joe, P. (2018). Radar Network–Based Detection of Mesocyclones at the German Weather Service. Journal of Atmospheric and Oceanic Technology, 35(2), 299-321,https://doi.org/10.1175/JTECH-D-16-0230.1

Imbert, J. (2019). Conception et évaluation d’un algorithme de détection automatique des mésocyclone. Rapport de stage de fin d'étude IENM.

Le Bastard T. (2022). Mesocyclone Detection at Météo-France, presented at ERAD 2022.

How to cite: Mathilde, M., Ludovic, B., Olivier, L., and Tony, L. B.: Characterization of thunderstorms to detect, track and extrapolate supercells., 12th European Conference on Severe Storms, Utrecht, The Netherlands, 17–21 Nov 2025, ECSS2025-259, https://doi.org/10.5194/ecss2025-259, 2025.

P39

ECSS2025-318

Updated satellite climatology of subtropical and tropical cyclones in the Mediterranean

(withdrawn)

Alois Martin Holzer and Pieter Groenemeijer