Nearly 40,000 people evacuated and displaced, 14 dead, more than 305 landslides having engulfed thousands of homes and half a thousand roads cut off. The balance sheet of deadly floods which have been hitting the Emilia-Romagna region in northwestern Italy for several days is heavy.
This Sunday, May 21, while the red alert was maintained until the end of the day, the head of the Italian government Giorgia Meloni returned to her country, shortening her participation in the G7 summit in Hiroshima, Japan, to face the crisis.
The very sudden rise in water levels on Friday afternoon after canals overflowed, submerged by the waters of flooding rivers, is the direct consequence of an increasingly frequent weather phenomenon, the cold drop.
“It is a pocket of very cold air located at more than 5,000 m altitude, explains one at Météo France. When the jet stream (jet-stream in English, very fast air current) polar deforms, it happens that a pocket is detached to descend to our latitudes, which is nicknamed a cold drop. It often causes disturbed weather, with showers, sometimes consisting of sleet to the ground, associated with strong gusts of wind. »
A rare phenomenon in spring
This is exactly what caused the very intense rainfall over Italy in recent days. “After crossing France and Switzerland, the cold drop deepened as it arrived in the Emilia-Romagna region and encountered the warm Mediterranean air, causing very heavy rain showers, up to 300 mm in only two days, explains Guillaume Séchet, meteorologist and founder of the site meteo-villes.com.
This type of phenomenon occurs more in the fall, and much more rarely during this spring period of the year when storms can be numerous, but not in this extreme form. »
As violent as it is unexpected in Italy, this phenomenon is no stranger to France. In June 2010, the Var department paid a very heavy price for what is called a Mediterranean episode, mainly in the watershed of the Nartuby and the lower valley of the Argens in the coastal zone. Result: 27 dead and considerable material damage.
So what are the risks today of seeing, in the days or weeks to come, a cold drop pouring out such a quantity of rain with, as a result, floods with dramatic consequences? “Not in the coming days and it is always difficult to predict long term, but yes, global warming and what is called tropicalisation of the Mediterranean climate increase the risk of seeing this type of event occur more often and more intensely, predicts Guillaume Séchet.
First in France and Spain, two countries that directly face the rising hot air from the Sahara. Mediterranean waters have remained exceptionally warm this winter and the “cauldron” effect is already present. »
The possibility of very heavy rains poses very serious concerns in the south-eastern region or in Occitania. Because, unlike northern Italy, where the soils are normally wet for the season, those of these two regions face historic drought. In the event of rain, they would be unable to absorb huge quantities of water and a disaster as deadly as that of the Var in June 2010 would then be highly probable.
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2023-05-21 17:27:00