There are some great papers regarding the statistics and cataloging of Mediterranean TCs.
A first paper by Leone Cavicchia, Hans von Storch and Silvio Guald uses the following criteria for Mediteraannean TCs.
*Only sea level pressure minima with pressure gradient greater than ∆P =20 Pa over 3 grid points are registered. So basically, on average a TC needs to be below 1013 - 20 = 993 mb to be registered.
*This pressure minima must have at least 6 hourly output steps -> TC for more than 6 hours. No more than half of the TC points can be above land.
*The TC must have traveled at least 200 km during its existence.
*A cyclone is classified as medicane if it shows vertical symmetry and a warm core for more than 10% of the track or more than 6 hours, calculated using phase space criteria.
*A cyclone is classified as a medicane if the wind speed averaged in a circle of radius 50 km around the pressure minimum is higher than 18 m/s (35 kt, 40 mph) for more than 10% of the track or more than 6 hours.
*A cyclone is classified as a medicane if the wind speed (averaged in a circle of radius 50 km around the pressure minimum) at 850 hPa is higher than the wind speed at 300 hPa.
*A cyclone is classified as a medicane if the maximum wind speed in a circle of radius 50 km around the pressure minimum is higher than 29 m/s (55 kt, 65 mph) for a time longer than 4 hours.
These requirements thus only look at storms with a pressure below ~993 mb and peak sustained winds of 55+ kt, besides some other requirements. These are way stricter requirements than we have for a TC in the Atlantic. Still, the paper found 99 medicanes over the period 1948 - 2011. If the requirement for the maximum speed drops from 29 m/s (55 kt, 65 mph) to 25 m/s (50 kt, 55 mph) the number of found TCs more than doubles for their smaller test dataset of 1995 - 1999.
Another paper by Nastos P.T., Karavana-Papadimou K. and Matsangouras I.T. (
https://cest2015.gnest.org/papers/cest2015_00407_oral_paper.pdf) found 65 medicanes over the period of 1947 - 2014. However, their requirement was continuous cloud cover, symmetric shape around a visible cleared cyclone eye. This sounds more similar to a hurricane requirement instead of a TC requirement.
In conclusion, the papers probably show that there have probably been roughly 65 hurricane-strength cyclones in the Mediterranean in 1947 - 2014 and that there have been 99 strong tropical storms with wind speeds of 55 kt or higher in 1948 - 2011. This is roughly 1 hurricane per year. However, it clearly shows that many more tropical storms and tropical depressions have formed. If you use the 21/9 ratio of TCs for the 50 kt and the 55 kt requirement then there could be upwards of 230 TCs in the dataset with wind speeds of at least 50 kt -> 3 - 4 per year on average. Lowering the requirement to 35 kt or 30 kt could cause this number to increase by a lot. I know the last two sentences use a lot of assumptions, but the bottom line is that there are clearly quite a lot of classifiable systems, most likely 5+ per year on average. I don't have access to the raw data unfortunately, but I'd love to see an analysis using a 30+ kt requirement to more accurately see how the Mediterranean compares to f.e. the Atlantic. I think a lot of people would be shocked how many TCs form in that basin while we are mostly just unaware of it.
