Medicanes Numa

Medicanes, short for “Mediterranean” + “hurricanes”, are cyclones over the Mediterranean Sea having a tropical-like structure but a rather small size.

They are relatively rare in Europe. They can be very destructive and deadly, even when they don’t reach their full potential for due to the combination of intense winds and heavy precipitation.

However, one such medicane are formed on 17 november 2017 strucked Greece killing at least 20 people and damaging 1,000 homes with flash floods and mudslides.

Copernicus Sentinel-3 captured, on 16 November 2017, the tightening surface low over central Mediterranean, which will form a Medicane on after day over the Ionian sea.

The image captured with SAR of Copernicus Sentinel-1 , show clouds swirling around a central eye. It’s the type of storm we’re accustomed to seeing in the tropical waters of the Atlantic and Pacific Oceans.

Medicanes passage over Ionian sea on 2017-11-17 H-16:37. In the gif there is the Wind Velocity extract from OCN products. Image from Sentinel-1 B DT00EBB3. Mosaic built with GDAL and Python2.7.

From the Level-2 OCN products of Copernicus Sentinel-1 we extracted the speed-wind : low speed in blue and strong speed in red, over the passage of Numa. The eye of the medicane appears darker in the SAR image and blue in the speed-wind image than its surrounding area because the wind speed at the centre of the medicane is lower.

Mediterranean cyclones are most likely to occur in the autumn, peaking in winter, and slowing down in the springtime.

Two regions in the Mediterranean are favourable for Medicane formation: the western part of the Mediterranean, between Spain and Sardinia and in the Ionian sea, to the west of Greece, is where Numa formed.

Like conventional hurricanes, they develop over warm waters. Where as Atlantic or Pacific cyclones require temperatures of around 80 degrees Fahrenheit to grow, medicanes have been known to evolve in waters as cool as 57 degrees.  Their formation depends on cool air above.

Although medicanes are expected to remain relatively rare, rising sea surface temperatures are expected to breed stronger medicanes in the future perhaps eventually turning them into full-blown hurricanes.

One of  the first description of this fenomena is in 1343, in his Istoria of the kingdom of Naples, Francesco Petrarca described one of the most violent storms that fell on southern Italy, particularly in the reign of Naples.

Concern the violent Mediterranean cyclones, he also talked to the astronomer, physicist and mathematician, Giuseppe Boscovich in 1749, in his operetta ‘ Above the turbine atmospheric that devastated a great part of Rome’, where after describing the violent tornado that knocks on the city eternal and and writes: “On our seas, at times, we saw storms similar to the terrible hurricanes of America; they are going to endure for a whole day or more, a great stretch of sea shatter “.

 

http://www.medicanes.altervista.org/
https://phys.org/news/2017-11-medicaneshurricane-like-storms-mediterranean.html

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