August 20, 2024

expert reaction to the superyacht capsizing off Sicily

Scientists comment on a yacht capsizing off the island of Sicily. 

Dr Jean-Baptiste Souppez, Senior Lecturer in Mechanical, Biomedical and Design Engineering at Aston University, and fellow of the Royal Institution of Naval Architects, said:

“The next 24 hours are crucial to hope and find survivors trapped inside. Superyachts such as the Bayesian are designed according to regulations that impose watertight subdivisions. The speed at which the vessel sank (a few minutes, according to survivor and witness accounts) and the fact that it remains intact and on its side could favour the formation of small air pockets inside. This is obviously highly speculative and impossible to predict accurately. There are records of survivors found in such air pockets: Harrison Okene’s rescue after three days trapped in an air pocket is well-documented thanks to the diver’s video of the rescue. Yacht races such as the Vendée Globe have seen competitor Jean Le Cam trapped inside his overturned yacht for 16 hours before another competitor could come to the rescue. A sign the rescuers may be looking for is a banging noise at regular intervals: this is common practice on submarines, and was one of the signs the search mission for the Titan submarine was looking for after it went missing last year. But whether air pockets formed on the Bayesian is simply impossible to predict.”

Dr Peter Inness, meteorologist at the University of Reading, said:

What is a waterspout?

“A waterspout is a narrow column of rotating air below a thunderstorm that occurs over water. They are part of the same weather “family” as tornadoes. Like tornadoes, many waterspouts are fairly inconsequential, with a few seconds of strong, gusty winds before they move on or dissipate. But some can be much stronger. Because they occur over water the damage is usually more limited than a tornado over land.”

How do they form?

“Waterspouts form beneath thunderstorm clouds, so need the same ingredients as a thunderstorm. Heat and humidity in the lower atmosphere are the two main requirements, and over the Mediterranean in late summer and autumn, there are plenty of both. Changes in wind direction with height are also needed to set up the rotation of air within the waterspout.”

How common are waterspouts?

“Waterspouts may be more common than tornadoes. Records are more patchy than for tornadoes though as many waterspouts go unobserved because they are over the sea.  The Mediterranean is possibly one of the places where waterspouts are most likely around the world due to the warm ocean surface and a climate that is very susceptible to thunderstorms throughout the summer and autumn. Many of the scientific studies of waterspouts have been located in the Mediterranean.

“A study by scientists from the University of Barcelona*, looking at waterspouts around the Balearic Islands, found that they are more likely when the sea surface is very warm. Currently the sea surface in the region of Sicily is about 2.5 to 3 degrees C warmer than the 1990-2020 average.”

*Vega, Moreno-Garcia and Guzman, Natural Hazards, 2022

What damage can waterspouts cause?

“The majority of waterspouts are quite weak, resulting in a short burst of gusty winds, which although momentarily quite strong cause little damage because they are over the sea. But at the more intense end of the scale, winds of above 100 km per hour are possible, although actual wind measurements from inside waterspouts are very rare indeed. Winds of this strength coinciding with the location of a boat are capable of causing damage or capsize, especially because the wind direction varies very rapidly within a waterspout which could cause a boat to rock violently.”

Declared interests: None.