What Is a Medicane? How Mediterranean Hurricane-Like Storms Form

Spanish authorities placed Catalonia under its highest rainfall danger level, 6 out of 6, on October 3, 2026, after forecasters identified the setup for a possible medicane forming off the coast. Catalan President Salvador Illa called the situation "very complex" and said "it is not a joke," describing the phenomenon to the public as a kind of mini-hurricane, according to Catalunyapress.es.

The Catalan meteorological service, Meteocat, classified the system as an exceptional mesoscale convective event, warning of up to 40 litres of rain per square metre in just 30 minutes, 90 litres in three hours and as much as 200 litres over 24 hours in some areas. Twenty coastal and inland counties, including Maresme, Barcelonès and parts of Girona and Tarragona, were placed under alert, while the southern Terres de l'Ebre region had already recorded 265 litres per square metre in L'Ametlla de Mar before being excluded from the latest warning, Catalunyapress.es reported.

What exactly is a medicane?

"Medicane" blends "Mediterranean" and "hurricane." It is not an official meteorological category used by agencies such as the US National Hurricane Center, but scientists use it to describe Mediterranean cyclones that behave like tropical storms rather than ordinary autumn low-pressure systems.

A 2024 study published in the Bulletin of the American Meteorological Society proposed a standard scientific definition: a medicane is a mesoscale cyclone over the Mediterranean Sea with a warm core reaching into the upper atmosphere, an eye-like feature at its centre surrounded by spiral cloud bands, and a nearly calm centre ringed by roughly symmetric wind circulation, with the strongest winds located only a few tens of kilometres from the core, according to the European Space Agency (ESA).

How does a medicane form?

Like tropical hurricanes, medicanes draw energy from heat and moisture evaporating off the sea surface, according to ESA. But the Mediterranean is far smaller and generally cooler than tropical ocean basins, so medicanes typically stay smaller and weaker than full hurricanes. ESA notes that not every medicane forms the same way: some develop mainly from that sea-heat engine, while others are triggered by mid-latitude weather patterns, such as an upper-level trough or a blocked jet stream, that push cold air over the relatively warm Mediterranean and destabilise the atmosphere.

The European Centre for Medium-Range Weather Forecasts (ECMWF) described this hybrid behaviour in its analysis of Medicane Daniel, the storm that caused catastrophic flooding in Greece, Bulgaria and Türkiye in early September 2023 before crossing into Libya. ECMWF said Daniel formed from a combination of a quasi-stationary upper-level trough over the Mediterranean, atmospheric blocking over Europe, and interaction with the remnants of Hurricane Franklin. Unlike a classic tropical cyclone, ECMWF noted, Daniel intensified further after reaching land, driven partly by high-altitude atmospheric forcing rather than ocean heat alone.

Why Daniel matters for scale

ECMWF estimated Daniel's winds could have reached 50 to 60 metres per second at their peak. After the storm crossed into Libya around September 9–11, 2023, two dams near the city of Derna burst following intense rainfall, and the resulting flooding killed between 5,000 and 15,000 people, according to ECMWF's figures. ECMWF's own assessment placed this disaster among the worst rainfall-triggered floods it has recorded during its operational-forecasting era, which the agency traces back to the late 1970s.

How rare are medicanes, and who is at risk?

ESA says medicanes form only up to about three times a year across the entire Mediterranean basin, making them far rarer than Atlantic hurricanes and difficult for scientists to observe and model. Despite their rarity, ESA estimates more than 500 million people live around the Mediterranean basin and could potentially be exposed to a medicane's impacts, which include intense short-burst rainfall, flash flooding, strong winds and rough seas rather than the sustained high winds typical of larger tropical hurricanes.

The current Catalonia alert

For the October 2026 episode, the most dangerous window ran from 8 p.m. on Saturday, October 3 through roughly 2 p.m. on Sunday, with conditions expected to improve by Sunday afternoon, Catalunyapress.es reported, citing Meteocat. The outlet said Spain's ES-Alert public warning system was activated for the affected counties as forecasters tracked the possible medicane's approach.