A rare, once-a-year medicane, that's a 'hurricane' in the Mediterranean sea, delivered solid surf, pumping to southern parts of Italy last week but also went on to be catastrophic for areas of Greece, a scene locals are describing as apocalyptic.
While Hurricane Teddy's busy doing its thing over on the US East Coast, storm Ianos was meandering across the tideless Med in a phenomenon you'll be lucky to see, let alone surf.
"Visiting tourists to the coastline of souther Italy would never guess that it is possible to surf here,” explains local surfer Marco Odoardi.
“However, once in a while a miracle happens. This storm originated very quickly almost out of nowhere. While moving from Libya to the east, it gained energy and brushed the south coast of Italy heading to Greece with destructive winds, forming a perfect ocean-like swell.
“I have been coming to this area for many years and only once have I seen such a good forecast. This time was different, I didn’t know what to expect. When I arrived there and saw the waves, I could not believe my eyes: powerful and pumping, with big and frequent sets.”
Alright, the pics throughout may not stand up to the rest of Europe's premier beachies, but this is southern Italy, a novelty amidst a region more akin to Sangiovese than surfing.
“The epic surf that occurred recently in Southern Italy was generated by an intense Mediterranean storm called Ianos,” adds MSW forecaster, Tony Butt. “Ianos tracked northwards from the Libyan coast and ended up a powerful storm in the Ionian Sea, between Italy and Greece. It was a classic example of a tropical-like storm that occurs in the Mediterranean: popularly referred to as a ‘Medicane’.
“Ianos started off as a depression over Libya around September 12. It then moved north out into the open sea on 13th and 14th, while drifting over an area of high sea-surface temperatures.
“This undoubtedly helped it develop, together with an area of contrasting air temperatures and a north-south pressure gradient associated with a high that had pushed in from the Atlantic.
Swell chart for the Med, HERE
“As a result, the system deepened rapidly on September 15 and 16, developing an area of gale-force winds on its northeast flank and pushing some large swell towards southern Italy.
“By the 17th, the storm turned eastwards, towards Greece. The light to moderate north and northwest winds on its western flank persisted over southern Italy while the swell arrived. The system didn’t back off; instead it made landfall in Greece, causing utter havoc with two people dead and around 1,000 rescued.”
But, how was this caused and why is it such a rarity? “In the case of Ianos,” Tony said, “the warm water almost certainly played a big part in helping the system to develop. In the same way as with ‘proper’ tropical cyclones and hurricanes, high sea-surface temperatures (SST) are a crucial factor in the development of the storm. The heat energy in the water is passed to the surface air, increasing convection and maintaining the vertical circulation, keeping the cyclone ‘engine’ going by constantly pumping energy into the system.
“With medicanes, SST doesn’t always need to be a necessary factor. For example, if the air in the upper atmosphere is particularly cold, this will have the same effect as a high SST, increasing the vertical instability in the atmosphere and keeping the ‘engine’ running. Vertical shear (= variation of wind with height) is also a big factor. Medicanes, along with other storms, don’t like too much shear, because it shear tends to ‘chop off’ the vertical circulation and short-circuit the system. So, the less shear the better.
“The fact that medicanes exist further south than typical Atlantic low pressures, means that they don’t need to look like dart boards to generate big surf. Why? Because of the Coriolis force (HERE). The windspeed around a cyclonic system – whether it be a medicane, a hurricane or a ‘normal’ low pressure – is proportional to the pressure gradient over the sea, but is also inversely proportional to the Coriolis force. Now, the Coriolis force increases with latitude; therefore, for any given pressure gradient between two points on the ocean, the lower the latitude the stronger the wind. If you want to dig deeper into this and feel the urge to do some maths, just look up the Geostrophic Equation.”
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How frequent are Medicanes and when do they occur? “A long-term climatological study of medicanes was done in 2014 by a group of scientists led by Dr Leone Cavicchia from the Euro-Mediterranean Centre for Climate Change in Italy. They analysed 60 years' worth of data and found that medicanes are actually not that frequent, with an average occurrence of 1.6 systems a year. They can form at any time of the year, as long as there is a strong difference between the surface and upper atmosphere temperature (even if SSTs are quite low). On average, most medicanes occur during autumn and early winter, and the least during spring.”