A Team of Researchers Sheds Light on the Atmospheric Phenomenon That Affected the Bayesian Superyacht

What sank the Bayesian superyacht off the coast of Palermo on 19 August 2024 was not a waterspout, but a meteorological phenomenon known as a 'downburst', characterised by strong downward gusts of wind. This is the hypothesis that emerges from an investigation by a group of researchers from the 'Antonio Righi' Department of Physics and Astronomy at the University of Bologna, as well as from CNR-ISAC, Agenzia ItaliaMeteo, ARPAE and PRETEMP.

The study, published in the Royal Meteorological Society’s journal Weather, analysed in great detail the weather conditions on the night of the Bayesian shipwreck, which claimed the lives of seven people.

"Both waterspouts and downbursts are relatively common phenomena in the Mediterranean Sea, especially between late summer and early autumn, when the warm sea provides the energy needed to develop intense atmospheric convection," explains Francesco De Martin, a PhD student at the University of Bologna and first author of the paper. "Our investigations show that the yacht may have been hit by a downburst, i.e. downward currents generated by some thunderstorms that can exceed 100 kilometres per hour and cause extensive local damage.

Measuring 56 metres in length and with a 75-metre aluminium mast (the tallest in the world), the Bayesian superyacht sank at 4:06 am on 19 August 2024 off Porticello, near Palermo, Sicily. Seven of the twenty-two people on board died as a result of the shipwreck. Excluding floods, it is the storm-related event that has claimed the most lives in Italy since 1970.

Initially, it was thought that the yacht may have been sunk by a waterspout, but no photos or videos have ever emerged to support this hypothesis, and there is no radar data from the area of the shipwreck.

"The atmospheric conditions on the night of 19 August 2024 were favourable for the development of waterspouts, due to the arrival of a cold front over the Tyrrhenian Sea and strong winds at high altitude, but these conditions can also cause downbursts," says Silvana Di Sabatino, a professor at the University of Bologna's 'Augusto Righi' Department of Physics and Astronomy who coordinated the study. "An analysis of the satellite images suggests that the second hypothesis is more likely."

As there was no radar data available for 19 August 2024 in the area of Western Sicily, the researchers based their analysis on satellite images, on data from a number of weather stations, and on videos posted on the web showing the weather conditions that night.

"The videos show the presence of strong linear gusts of wind, but overall no clues emerged to suggest the presence of a waterspout," explains Mario Marcello Miglietta, research director at CNR-ISAC and one of the authors of the study. "In the absence of elements in favour of the waterspout hypothesis, the meteorological phenomenon most likely to have hit the Bayesian was a downburst."

The researchers also sought to understand how predictable the storm that hit the yacht was, pointing out that the day before the event, weather models indicated the possibility of thunderstorms associated with strong gusts of wind in the area. The Civil Protection had in fact issued a yellow alert for thunderstorms on the coasts of northern Sicily.

"This tragic episode has highlighted, on the one hand, how exposed Italy is to the risks associated with strong, localised thunderstorms and, on the other, that an early warning system in areas exposed to these phenomena is possible," confirms Francesco De Martin. "We are aware that in the case of thunderstorms it is more difficult for citizens to understand a warning correctly, but the Bayesian teaches us that we should never underestimate these phenomena and that it is best to take all necessary precautions."

In order for the warning system to remain effective – the researchers suggest – an effort is needed on the part of the institutions, both to enhance the ability to forecast and monitor severe storms, and to improve the communication of warning signals to citizens.

The study was published in the Royal Meteorological Society’s journal Weather with the title "The Bayesian sinking in Porticello: a predictable convective windstorm?". The authors are Francesco De Martin, Michele Martinazzo, Matteo Siena and Silvana Di Sabatino from the 'Augusto Righi' Department of Physics and Astronomy at the University of Bologna, together with Mario Marcello Miglietta from CNR-ISAC, Federico Pavan from the PRETEMP group, and Thomas Gastaldo from Arpae Emilia-Romagna and Agenzia ItaliaMeteo.