Catalonia studies whether the October 'minihurricane' was the first tropical cyclogenesis in the Mediterranean

Meteorologists are investigating whether the storm that caused two deaths and one missing person in Catalonia was the first recorded pure tropical cyclogenesis in the Mediterranean, a phenomenon with no known precedents.

The torrential rains that hit Catalonia in early October, with historical records such as 288 litres per square metre in Vilassar de Mar, 248 in Granollers, 244 in Mataró, and 213 at the Can Bruixa station in Barcelona, may have been more than just an extreme storm. According to 20minutos, meteorologists are considering the hypothesis that it was the first pure tropical cyclogenesis ever observed in the Mediterranean.

Researcher Carlos Calvo-Sancho from the Climatoc-Lab at the Centre for Research on Desertification (CIDE), a mixed centre of CSIC, Universitat de València, and Generalitat Valenciana, explains that for a 'medicane' to form, there is usually a disturbance at high levels that detaches from the general circulation. However, in this episode, there was no such disturbance. What existed was the Mediterranean at 25-26 degrees Celsius, the threshold defined for tropical cyclogenesis in the Atlantic.

"The hypothesis is that this very high anomaly in the Mediterranean allowed the development of this convective system and that it was the beginning of a pure tropical cyclogenesis in the Mediterranean. Something never seen before," says Calvo-Sancho.

The scientist, who received the EMS Young Scientist Award 2026 from the European Meteorological Society, emphasises that it is now necessary to analyse whether the phenomenon had a baroclinic component at high levels or if, on the contrary, it lacked one. "If the hypothesis is confirmed, it would be the first time it has occurred in the Mediterranean," he agrees.

These tropical systems are different from the already recorded explosive cyclogenesis, which are "traditional extratropical cyclones", but "very similar" to 'medicanes', a term that combines Mediterranean and hurricane and has been common in the area since satellite measurements began in the 1970s. "Medicanes are, after all, the same as a tropical cyclone or hurricane, but smaller, because the Mediterranean is not as large as the Atlantic or the Pacific," he points out.

The key difference, according to the researcher, is that in a typical 'medicane' there is a tropical transition from a pre-existing extratropical cyclone. "But this time you don't have that baroclinic precursor; instead, it is directly as if it were tropical, as if it were purely tropical. That is the difference," he details.

In the same vein, meteorologist from the State Meteorological Agency (Aemet) Juan Jesús González Alemán stated on October 4 on the social network X that "a more in-depth study will be needed, but it increasingly crosses my mind, seeing the radar and satellite animations and what the models suggested, that the extreme episode that has affected Catalonia in recent hours is more consistent with a tropical cyclogenesis process."

"This has no known precedents in the Mediterranean. It has not been and is not a 'medicane' or 'minihurricane' (something that, by the way, does not physically exist), nor was it what appeared in the models. It does not fit the typical conceptual model of 'medicane' in the Mediterranean: this is something different, a process of tropical cyclone formation like those that occur in the tropics," González Alemán added.

The meteorologist shared a satellite image of the phenomenon before it reached the Catalan coast. "If I remove the coastlines, any expert in tropical meteorology would say it belongs to the tropics. And this would open a new debate in the scientific community," he pointed out.

The storm, which President Salvador Illa described as a "mini-hurricane", left two dead, one missing young person, flooding, sudden river rises, and overflows in various parts of Catalonia. The hypothesis of a pure tropical cyclogenesis, if confirmed, would require a review of prediction models and alert protocols in the Mediterranean.

Meanwhile, scientists continue to analyse the data to determine if there was indeed a baroclinic forcing that allowed the system's development. The answer could come in the coming weeks when ongoing studies are published.