Mediterranean tropical-like cyclones, sometimes referred to as Mediterranean hurricanes or Medicanes, are rare meteorological phenomena observed in the Mediterranean Sea.
Due to the dry nature of the Mediterranean region, the formation of tropical and subtropical cyclones is infrequent, with only 100 recorded tropical-like storms between 1947 and 2011. Most systems remain at or below tropical storm intensity, but on a few rare occasions, some storms have been observed reaching the strength of a Category 1 hurricane. No agency, however, is officially responsible for monitoring the formation and development of Medicanes.
Tropical cyclogenesis typically occurs within two separate regions of the sea. The first region, encompassing areas of the western Mediterranean, is more conducive for development than the other, the Ionian Sea to the east. However, on very rare occasions, similar tropical-like storms may also develop in the Black Sea.
The rough mountainous geography of the region raises additional difficulties despite being favorable for the development of severe weather and convective activity in general, and only with abnormal meteorological circumstances can Medicanes form. Numerous studies have been conducted on the impact of global warming on Mediterranean tropical cyclone formation, generally concluding that fewer yet more intense storms would form.
The development of tropical or subtropical cyclones in the Mediterranean Sea can usually only occur under somewhat unusual circumstances. Low wind shear and atmospheric instability induced by incursions of cold air are often required. A majority of Medicanes are also accompanied by upper-level troughs, providing energy required for intensifying atmospheric convection—thunderstorms—and heavy precipitation.
The baroclinic properties of the Mediterranean region, with high temperature gradients, also provides necessary instability for the formation of tropical cyclones. Another factor, rising cool air, provides necessary moisture as well. Warm sea surface temperatures (SSTs) are mostly unnecessary, however, as most Medicanes’ energy are derived from warmer air temperatures. When these favorable circumstances coincide, the genesis of warm-core Mediterranean tropical cyclones, often from within existing cut-off cold-core lows, is possible in a conducive environment for formation.
The development of tropical-like cyclones in the Mediterranean can occur year round, with activity historically peaking between the months of September and January of the following year.
Several notable and damaging Medicanes are known to have occurred. In September 1969, a North African Mediterranean tropical cyclone produced flooding that killed nearly 600 individuals, left 250,000 homeless, and crippled local economies. A Medicane in September 1996 that developed in the Balearic Islands region spawned six tornadoes, and inundated parts of the islands. Several Medicanes have also been subject to extensive study, such as those of January 1982, January 1995, September 2006, November 2011, and November 2014.
The January 1995 storm is one of the best-studied Mediterranean tropical cyclones, with its close resemblance to tropical cyclones elsewhere and availability of observations. The Medicane of September 2006, meanwhile, is well-studied, due to the availability of existing observations and data. In November 2011, the NOAA’s Satellite Analysis Branch monitored a Medicane, named Rolf by the Free University of Berlin (FU Berlin), though it ceased doing so the following month. In 2015, the NOAA resumed issuing advisories for tropical systems in the Mediterranean region.