To cause the sinking of the Bayesian Yachts off the coast of Little Port (PA) in the early hours of the July 19, 2024 it would not have been a waterspout on the sea, that is, a waterspout, but a downburst (which in Italian could be translated as “burst downwards”), a meteorological phenomenon associated with storm clouds in which a strong current of cold descending air impacts the ground producing linear bursts at very high speed (even over 180 km/h depending on the size of the burst). The two phenomena are often confused, but their dynamics and origin are different. This hypothesis is supported by a video taken by a surveillance camera in the area around the time of the shipwreck, in which intense gusts of wind can be seen knocking down some umbrellas in the same direction, thus indicating linear winds and the absence of the vortex motion that is instead characteristic of tornadoes.
What are downbursts and how do they form?
THE downburst They are currents that descend in a very violent from a storm cloud and that is spread rapidly in every direction as soon as they hit the ground.
To have a downburst you first need a cumulonimbusthat is, a thundercloud. These clouds have a strong vertical development in the presence of ascending currents due for example to very hot and humid air at the ground (as in the case of so-called “heat storms”). To maintain the balance, these currents are associated descending currents (in slang downdraft) that bring cold, dry air to the ground at high altitude. At the same time, they can develop flows that introduce drier air in the part central And inferior of the cloud.
At this point a sort of “tug of war” begins between the ascending currents and the descending ones. It can happen, for example, that the former are so intense that they keep a large quantity of rain suspended in the central and upper part of the cloud. But at a certain point there is a limit: when the ascending currents are no longer able to suspend the accumulated rain, it falls to the ground all at once, dragging with it large amounts of air which reinforce the downdraft by “crashing” it to the ground very quickly: this phenomenon, which typically lasts 20 to 30 minutesit is precisely the downburst.
Downbursts and tornadoes: the differences and how to tell them apart
While downbursts are air currents that fall, impact the ground and diverge linearly in all directions, tornadoes have a typical funnel-shaped appearance and show a vortex motion: the air rotates very rapidly, with speeds of up to 300 km/h. This is because within the cumulonimbus or thunderstorm cell the air swirls around a central low pressure and the column of air below this low pressure can follow this circular motion. In some ways, tornadoes are less dangerous than downbursts because they only cause damage in the area below the vortex column, whereas the effects of a downburst can affect several square kilometers.
Precisely because of the different dynamics between the two phenomena, distinguishing them is quite simple especially after their passage. If the debris is arranged radially, i.e. “fan-shaped”, and locally has the same direction, then it was a downburst; if instead the debris is arranged circularly we are in the presence of a whirlwind.
