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A Medicane is a cyclonic storm system similar to a Hurricane which is related to subtropical cyclone. Even tough the Mediterranean sea is not a official Basin, and thus not under the authority of any major Storm Center like the National Hurricane Center, there are occasionally Cyclones forming along the mid-latitudes, having properties of a tropical cyclone. It is very narrow, has an axisymmetric cloud structure generates strong winds and heavy rains. This phenomenon has often been named Medicane or storm Mediterranean TMS (Tropical Storm Mediterranean-like) type by the media strongly influenced by information from the Anglo-Saxon meteorological agencies. With global warming, such an extreme phenomenon could become more frequent.

Origin of the phenomenon

Almost every year, usually in the fall when the Mediterranean Sea is still warm, a depression takes on the characteristics of a subtropical storm with clouds wrapped around an eye, intense thunderstorm activity, strong winds at the surface and warm temperature in the center clouds. On a satellite image, such a system can be very close to that to what tropical storms look without having the dimensions nor the power. It may have a diameter between 300 and 420 km (186 to 261 miles). The cyclone can possibly intensify with winds that can reach over 130 km/h (80mp/h) .

Research shows that the surface temperature of the sea at must at least be 20° C (68° F) for the development of these systems and the Mediterranean Sea reaches 24-28° C (75° F - 82° F) from late August to mid-September. However, the seasurface temperature is not as critical as for a purely tropical system that depends on the release of latent heat in a uniform air mass. Indeed, an influx of cold air aloft, from the continent, makes the air mass unstable and gives convection. The storm form at a cut-off low altitude and it is mainly the difference between the temperature of the sea and altitude that is important. So this is a mix of tropical and frontal effect.

Lifecycle

The analysis of several cases shows, that these weather systems pass through different stages: development, stationary phase and formation of an eye. The systems begin with the development of convective clouds near a low pressure center, heavy rains and thunderstorms.

It is only in the second phase as thunderstorms completely surround the center of rotation and forms an eye. At this point, the system is more or less stationary and winds increase to over 40 km/h (25 mp/h). Finally, the storm begins to move quickly, 37 km/h (23 mp/h) on a well defined path and winds exceeding 80 km/h (50mp/h), while the rate of precipitation generally decreases except when passing over land.

Cases

The majority of cases were reported in the western Mediterranean in autumn  :

   September 1947;
   September 1969;
   January 1982;
   September 1983;
   from 14 to 18 January 1995 in the central Mediterranean;
   from 11 to 13 September 1996, in the western Mediterranean;
   from 3 to 6 and 7 to 10 October 1996 in the western Mediterranean ;
   from 6 to 11 October 1996 in western and central Mediterranean;
   from 25 to 28 May 2003, in the western Mediterranean;
   from 17 to 19 October 2003, in the western Mediterranean;
   from 26 to 29 October 2005, in the central Mediterranean;
   from 13 to 16 December 2005 in Central and Eastern Mediterranean;
   from 6 to 9 November 2011, in the western Mediterranean;
   from 27 to 29 October 2012, in the western Mediterranean.

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