Observations and model simulations of a winter sub-synoptic vortex over the central Mediterranean

A sub-synoptic vortex. with characteristics of a tropical storm developed over the area between Italy and Greece, during the period 14-18 January 1995. Satellite imagery revealed that this vortex was associated with spirally distributed bands and a clearly defined 'eye'. Ship reports and SSM/I retrieved winds show the existence of strong surface winds around the vortex. Simulation of the genesis and life-cycle of the vortex using the Regional Atmospheric Modelling System and the Eta model successfully reproduced the vortex formation, its strength and its path towards the northern African coast. The model results showed the importance of the surface fluxes (sensible and latent heat) in the development of the vortex on the rear side of a parent low-pressure system which was advected towards the east. During the mature stage of the vortex, latent-heat release within the convective motions was the dominant mechanism which sustained the vortex until its landfall.