Increasing evidence shows that the Mediterranean is one of the regions in the world most affected by climate change. Scientific studies warn that the frequency of extra-tropical storms in the Mediterranean Sea, known as ‘Medicanes’ or ‘Mediterranean Hurricanes’, could become more frequent due to human-induced climate change. These hurricanes can have a devastating effect on communities and tourism.
A medicane is a tropical-like cyclone that forms over the Mediterranean Sea and may bring serious weather to areas of southern Europe. They form during the development of a warm front and need a certain minimum temperature (at least 26 Celsius on sea surface) and vertical wind shear (the change of wind speed or direction with increasing heights).
With the surrounding dry climate and the relatively shallow waters of the sea, the occurrence of tropical-like cyclones is infrequent. They typically form in the fall or winter months and occur once or twice a year.
On September 18, 2020, a medicane named Lanos made landfall along the coast of Greece and caused heavy rainfall and flooding in Greece and surrounding islands.
The geography of the Mediterranean region, as well as its dry air, typically prevent the formation of tropical cyclones, when certain meteorological circumstances arise, difficulties influenced by the region's geography are overcome.
These occur more in relatively colder waters than tropical cyclones, hurricanes and typhoons. Hence, the cores of these storms are also cold, as compared to the warm cores of tropical cyclones (but warmer as compared to extra-tropical cyclones).
These are typically smaller in diameter and have lower wind speeds than true tropical cyclones.
Sometimes, warm-cored tropical cyclones transform into cold-cored extratropical cyclones and in rare cases, the opposite can also happen.
Studies show an increase in number during the 1980s, 1990s and 2000s. But the total number was about 20 in the 2010s and more than 25 in the 2000s. It is however apparent that a warm Mediterranean is experiencing more of these storms.
Two of these storms, one in 2005 and another in 2012, even formed over the Black Sea, which is a much smaller water body than the Mediterranean Sea.
Due to global warming, warmer sea surface temperatures in the Mediterranean can allow the storms to take on more tropical appearances and characteristics, increasing the wind speeds and making the storms more intense and cause heavier rainfall.
This year is a mild La Niña, according to the World Meteorological Organization. La Niña is the cooling phase of the El Niño Southern Oscillation (ENSO) cycle in the equatorial Pacific Ocean, as opposed to the warming El Niño phase. It is characterised by the unusual cooling of the central and east-central equatorial Pacific Ocean.
A La Niña produces more rain in the central eastern part, where most of the Mediterranean cyclones develop. The slopes and the convection rising from sea waters can combine to spin off these cyclonic storms that become a Medicane if the 10-minute average wind speeds are greater than 99 km / hr.
