Defining Medicanes: Bridging the Knowledge Gap between Tropical and Extratropical Cyclones in the Mediterranean

The term “Mediterranean tropical-like cyclone” or “medicane” has been used in different ways by different authors. Identification of medicanes has been based on features observed from satellite imagery or on diagnostics applied to numerical weather prediction model outputs. In the absence of an official definition, medicanes are generally considered to be cyclones over the Mediterranean sharing physical processes with tropical cyclones. Nevertheless, recent studies on the dynamics of several systems widely recognized as medicanes show different underlying development mechanisms. A commonly agreed definition is critical and necessary to assess their climatology in past and future climates, as well as to consistently identify such systems in weather forecasts. The scientific community working on Mediterranean cyclones hereby proposes a definition, which is based solely on Earth observations: “A medicane is a mesoscale cyclone that develops over the Mediterranean Sea and displays tropical-like cyclone characteristics: a warm core extending into the upper troposphere, an eye-like feature in its center with spiral cloud bands around, an almost windless center surrounded by nearly-symmetric sea surface wind circulation with maximum wind speed within a few tens of km from the center.”. SIGNIFICANCE STATEMENT: Nearly two decades have passed since the term “medicane,” short for “Mediterranean hurricane,” has become commonly accepted to represent Mediterranean vortices with satellite-observed characteristics typical of tropical cyclones. The absence of an official or commonly accepted definition has created some confusion within the scientific and operational community. To overcome this ambiguity, here, we propose a phenomenological definition that can serve as a reference for future scientific research and operational applications, to be applied to any cyclonic system in the Mediterranean that bears structural similarities to tropical cyclones. This simple definition will assure consistency and, at the same time, can be used with the outputs from numerical models, working as a reference for future scientific research or operational applications.