Environmental conditions favorable to the development of a wet downburst in a Mediterranean region

Résumé fourni par la source

On July 10, 2019, a severe windstorm occurred in southeastern Italy, causing one fatality and severe damage. At approximately 17:10 UTC, the downburst crossed the port of Taranto, pushing an employee working on a crane in the Ilva steel plant under water. Unfortunately, the consequence of the event recalls that of an EF3 tornado that occurred on November 28, 2012, which was responsible for the death of another employee working exactly on the same crane. Observations suggest that the event was a microburst that crossed the Ionian coast of the Apulia region. The environment over the Ionian Sea, where the downburst developed, was characterized by intense deep-layer wind speed shear but limited directional shear and strong conditional instability. Mid-level humidity was reduced by dry air transported from the Sahara Desert toward southern Italy. Numerical simulations with a mesoscale model show that it is possible to produce a simulated windstorm with a trajectory and evolution like the real one. The genesis of the downburst was favored by some mesoscale meteorological features: the cold and dry low-level air following a cold front reduced the convective inhibition and initiated convection over the Ionian Sea, while the unidirectional wind profile favored the possibility of downburst development. Finally, the differences in environmental conditions with the case of November 2012 are discussed.

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