Mediterranean ‘medicane’ storms and the climate future

Once every year or two, people living along the Mediterranean Sea hear the forecast for a “medicane,” a hybrid storm that – while not truly a tropical cyclone – delivers some of the same weather impacts that hurricanes and cyclones do.

This time it’s affecting Greece, and the medicane called Ianos is expected to be unusually intense. The Hellenic National Meteorological Service, the country’s weather agency, issued a red-alert warning for the southern Ionian and Peloponnese regions for Thursday night with storm-force winds, heavy seas and torrential rains. The storm will continue to impact Greece through the weekend.

But what will these medicanes be doing in the future? Climate change is driving research into how tropical storms behave in a world of rising sea levels and temperatures that raise the risk of coastal inundation, wind damage and excessive rainfall.

Less is known, though, about how the Mediterranean storms will respond. In fact, the NOAA agency in the United States said in May that its GEOS Forward Processing (FP) system is only now advanced enough to analyze and forecast this kind of system, which was theoretical in the modeling as recently as five years ago. Their first successful effort using the GEOS FP system was just last year, when Mediterranean storm “Trudy” formed on November 11, 2019 and landed the same day along the Algerian coast. European scientists have encountered similar challenges in understanding the ingredients of these storms and how to forecast them.

“A number of papers have shed some light on the mechanisms of formation and intensification (but) several questions are still the subject of debate in the scientific community,” says Italian scholar Mario Marcello Miglietta. These questions include how to even define the so-called medicane in the Mediterranean, which is already identified as a hotspot for climate change.

A 2019 study from the Environmental Sciences Institute at the University of Castilla‐La Mancha in Spain offers some insights on what to expect by the end of the century. They based their findings on the middle-of-the-road RCP4.5 global warming scenario, with temperature rises between 2 and 4°C.

There are likely to be fewer storms, in keeping with a global trend that extends to fully tropical systems too. The increases in sea surface temperatures and other conditions will contribute to heavier rains and stronger storms primarily in the latter part of the century.

“Medicanes are likely to become more vigorous in autumn relative to spring and winter and to develop long‐lasting deeper warm cores, that is, more robust tropical structure, increasing the likelihood of achieving hurricane intensity,” said the paper authors, led by Juan J. González‐Alemán.

The storm tracks are likely to shift south and east in the Mediterranean, they add, with far more common occurrences in the Ionian Sea – right where the current storm impacting Greece can be found.