Medicane Daniel : a numerical model evaluation study
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Date
2025-06-20
Authors
Χαντζιάρα, Αμαλία Νικολέτα
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Abstract
The present thesis was conducted at the Laboratory of Atmospheric Physics (LAPUP) οn the Department of Physics, University of Patras. It constitutes an in - depth study of the Mediterranean hurricane Daniel, is the Greek region during September 2023. The high sea surface temperatures (SSTs) of the Ionian Sea, were responsible for the transfer of latent heat and moisture, favoring cyclogenesis. At the same time, the interaction with a pre - existing cut - off Low Pressure System (LPS) in the upper atmosphere supported the dynamic vertical development of the system. Storm Daniel was characterized by increased symmetry, a warm - core, a spiral cloud pattern, and moderate winds around its “eye”; where clear skies and cloudless conditions prevailed. The presence of the system caused a significant drop in atmospheric pressure and temperature across the country, accompanied by high values of relative humidity. Additionally, continuous extreme precipitation affected areas of Thessaly and Central Greece. The resulting flooding led to drowning and displacement of people and animals, destruction of infrastructure and roads, as well as damage to large cultivated areas and agricultural equipment. On September 06 2023, the system began to weaken due to the deterioration of its vertical structure and moved southeast towards Libya. This study aims to highlight the importance of understanding the structure and evolution of medicane Daniel as a fundamental prerequisite for more effective simulation and forecasting intense weather phenomena.
More specifically, Chapter 1 presents a theoretical review of the main types of cyclones, their characteristics, and the stages of their development. Special emphasis is given to Mediterranean cyclones (medicanes), which, although rare, are responsible for the majority of severe rainfall events in the Western Mediterranean.
Next, Chapter 2 describes the type of data and the methodology followed. Data from in - situ measurements (METARs) and atmospheric soundings from meteorological monitoring stations in the country were utilized, while rainfall data were obtained from the Hellenic National Meteorological Service (HNMS). Complementary reanalysis data from the ERA5 database of Copernicus were also used, covering both surface and upper atmospheric layers. The simulation of the phenomenon was performed using a Numerical Weather Prediction (NWP) model, the Weather Research and Forecasting (WRF) model, while its evaluation was based on comparison with observations and gridded data.
Chapter 3 focuses on examining the system’s evolution from its surface to the upper tropospheric levels. Variables such as pressure, temperature, relative humidity, wind, and precipitation are analyzed in conjunction with the assessment of the WRF model’s forecasting skill. Particular attention is paid to the accuracy of the modeled spatial and temporal distribution of the phenomenon.
Chapter 4 summarizes the main findings of the study, focusing on the capabilities and limitations of numerical simulation in capturing intense meteorological phenomena such as medicane Daniel. Points of convergence and divergence between the model and observations/gridded data are highlighted, while proposals for improvements in future applications are also included. Finally, extensions of the current analysis are presented, such as performing different simulation schemes and using an extended network of meteorological stations, with the ultimate goal of enhancing forecasting skill and achieving more accurate representation of the medicane Daniel.
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Keywords
Mediterranean hurricane, Precipitation, Numerical weather prediction