Ciao Amici,
Alex demonstrates perfectly the tropical transition, of a extratropical cyclone into a tropical cyclone over temperate water.
Subtropical Storm Alex developed over 21.5°C sea surface.
Hurricane Alex phase occured on 20-17°C sea surface;
Probably Hurricane Karl Nov. 1980 developed over 18-20°C sea surface;
(NHC: It is very unusual to have a hurricane over waters that are near 20 C, but the upper-tropospheric temperatures are estimated to be around -60 degC, which is significantly colder than the tropical mean. The resulting instability is likely the main factor contributing to the tropical transition and intensification of Alex).
Alex shows that the Mediterranean cyclones that occurred in January 1982 and 1995 (17-18°C sea surface) are the same as Atlantic tropical systems (such as those in other months)..
Do not forget to Alex when talking 'of tropical cyclones over the Mediterranean sea.
Daniele