On the role of large scale and air–sea interaction in a winter Mediterranean tropical-like cyclone Jolina

A Mediterranean cyclone affecting North Africa and Libya was investigated through a set of numerical experiments designed to disentangle the roles of large-scale dynamics, air-sea interaction, and sea surface temperature (SST) structure. Simulations were performed with the WRF model, including an ocean mixed layer (OML) scheme with a prescribed depth of 40 m, consistent with observed conditions. Atmospheric initial and boundary conditions were provided by ECMWF IFS analyses at 6hrs intervals. The cyclone started as an extra tropical cyclone and developed as a warm seclusion system leeward of Tunisia, primarily driven by synoptic scale forcing and orographic effects rather than local thermodynamic feedbacks. Two baseline low-resolution simulations using global model SST were compared with four convection-permitting experiments (1.5 km grid spacing) forced by high-resolution CMEMS SST fields. These simulations, performed with and without spectral nudging, include sensitivity tests to the SST field (i.e., mesoscale SST anomaly removed). Results show that the cyclone track and propagation are largely controlled by the large-scale trough, with only limited local deviations associated with convective bursts. Spectral nudging exerts a secondary influence, slightly improving the alignment with the large-scale flow but inducing only minor changes in the trajectory and landfall timing. The role of air–sea interaction is primarily manifested in the cyclone morphology, propagation speed, and, to a lesser extent, intensity, with differences in minimum sea-level pressure of the order of 2-4 hPa across experiments. On the other hand precipitation is strongly modulated by SST structure. The presence of mesoscale SST anomalies enhances precipitation by more than 25%, highlighting the importance of fine scale air-sea interaction for convective processes. Removal of SST anomalies leads to reduced precipitation and a less organised convective system, despite relative limited impact on the overall cyclone path. These results indicate that, while the system exhibits some tropical-like features, its evolution is predominantly governed by large-scale dynamics, with air-sea interaction playing a secondary, but non-negligible role, particularly for precipitation processes.