What is a waterspout, which may have sunk the luxury yacht off Sicily?

First, who was on the yacht?

The yacht was carrying 22 people, including 12 passengers and 10 crew members, when the storm hit.

Among the six people still missing is 59-year-old tech entrepreneur Mike Lynch, known as the “British Bill Gates”, according to a report by the BBC. Lynch is the founder of software giant Autonomy (established in 1996) and has been a science adviser to David Cameron when he was prime minister. In June, the entrepreneur was cleared of accusations that he had defrauded US company Hewlett-Packard in 2011 when he sold Autonomy for $11 billion.

Lynch’s daughter, Hannah Lynch, is also among the six people missing. His wife, Angela Bacares, was rescued on Monday.

What are waterspouts?

A waterspout is a large column of air and mist rotating over a water body. It is a weaker cousin of tornadoes and typically lasts for around five minutes — occasionally it can last up to 10 minutes. The average waterspout can be around 165 feet in diameter, with wind speeds of 100 kilometres per hour.

Although waterspouts are more common in tropical waters, they can appear anywhere. They occur when there are high levels of humidity and relatively warm water temperatures compared to the overlying air.

What are the types of waterspouts?

There are two types of waterspouts: tornadic waterspouts and fair-weather waterspouts.

Tornadic waterspouts are actual tornadoes that form over water or move from land to water. “They are associated with severe thunderstorms, and are often accompanied by high winds and seas, large hail, and frequent dangerous lightning,” according to a report by the US agency National Oceanic and Atmospheric Administration (NOAA). Tornadic waterspouts can be large and may lead to considerable destruction.

Fair-weather waterspouts, which are much more common, form over only water. As their name suggests, they are formed during fair weather. They are less dangerous and usually small.

According to a report by The Guardian, the waterspout that hit Lynch’s appears to have been a tornadic waterspout.

Is the frequency of waterspouts increasing in recent years?

Yes, experts believe that as ocean temperatures are soaring, the frequency of waterspouts is increasing.

Dr Peter Inness, a meteorologist at the University of Reading, in an interview said, “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 Celsius warmer than the 1990-2020 average.”