Analisi del ciclone Apollo e la sua possibile transizione a Medicane durante la sua fase matura tra il 26-29 Ottobre 2021, usando il modello WRF.

Depressions with a similar structure to tropical cyclones, that can reach the intensity of a hurricanes, are occasionally generated in the Mediterranean sea. Such phenomena are called Medicanes (from Mediterranean Hurricanes) or Tropical Like Cyclones (TLC). Although the geographical dimensions of tropical oceans and the Mediterranean sea are clearly different, the precursor mechanism of these perturbations, based on the air-sea thermodynamic imbalance, are similar. Some clues that may point to this transition are: the size of the cyclone and the clear existence of an eye. Considering previous studies that have examined some particular cases of Medicanes, the criteria which Medicanes must meet are: 1)the existence of a well defined eye, 2)the symmetry of the cloud mass around the eye; 3)the continuity of the cloud mass, 4)a diameter lower than 300 km, 5)a duration exceeding 6 hours. On 24-25 October 2021 a Mediterranean cyclone, lately named “Apollo”, formed in the Mediterranean sea and caused significant floods in Sicily, Algeria, Tunisia and Libya. The objective of the thesis is to check if this cyclone met the criteria needed to be classified as a Medicane or a TLC, then eventually analyse the mechanism that led to the formation of the Medicane and focus on when and how long the cyclone has been a TLC. I decided to use the Index Genesis proposed by [1]Tous and Romero (2011) to search the ideal conditions for the transition to TLC, comparing the results to certified cases of Medicanes (Rolf, 2011). In absence of data in the sea I used the WRF Software to simulate the event with initial data provided by GFS model. The satellitary images were used to identify the eye of cyclone. At first I simulated the Rolf Medicane studied in 2013 comparing our results to previous studies, in order to be sure that the current version of WRF (4.1.2) was able to simulate such kind of phenomena. Then, I performed the simulation for the Apollo case and studied the event focusing on the genesis, the decrease of pressure, the sea surface temperature and the wind speed. I focused analysis by examining some of threshold parameters such as concentric pressure at different levels, wind speed and Index Genesis. After this, I varied some initial meteorological conditions to identify the environments parameters that favored the genesis and development of this Mediterranean cyclone. I focused my analysis on the Sea Surface Temperature (SST) and how the cyclone change its trajectory and intensity.