Over two feet of rain fell in Italy in only half a day, something not seen in Europe before

CNN

By Pedram Javaheri, CNN

Extreme, climate-fueled rainfall broke records this week in a part of Italy known for its rain and an area in Oman not known for rain at all.

On Monday, a series of storms put on the parking brakes over northwestern Italy, unleashing rainfall rates never before seen in all of Europe after over 29 inches (742 mm) of rain fell in just 12 hours. In Oman, a rare tropical cyclone dumped years’ worth of rainfall, bringing deadly floods to the desert landscape that rarely sees much rain in an entire year.

Feet of rain in half a day

Italy’s Genoa province, known for its natural beauty and rugged coastlines, became the epicenter for the most recent extreme rains.

A series of slow-moving storms stalled in the region Sunday into Monday, dumping over 36 inches (925 mm) of rain in the town of Rossiglione, about 60 miles (100 km) southwest of Milan.

For some context, 36 inches is roughly equivalent to the average rainfall one would expect in Seattle in a year. It would take London an average of 15 months to tally such rainfall. Dozens had to be rescued after reports of mudslides and flooding dotted the landscape, leading a bridge to collapse in the town of Quiliano, according to Milan news outlet Corriere della Sera.

Wet weather is not uncommon in this part of Italy, as the region averages over 50 inches (1,200 mm) of rain per year. However, the storm dropped nearly 30 inches (750 mm) in just 12 hours, setting a new European mark for the highest 12-hour rainfall on record, according to climatologist and extreme weather expert Maximiliano Herrera.

In the nearby town of Cairo Montenotte, about 20 miles (32 km) west of Rossiglione, weather records continued to fall by the wayside on Monday. A 6-hour deluge unlike any ever observed in Italy brought nearly 20 inches (500 mm) of rainfall, besting the national 6-hour record for all of Italy, Herrera noted.

Just a few miles to the east, the mind-bending rainfall also inundated the nearby town of Vicomorasso, after over 7 inches (180 mm) fell in just one hour, according to FloodList, an organization that documents significant flood events from around the world.

By comparison, remnants of Hurricane Ida swamped Central Park in early September after a record of 3.15 inches fell in just 1-hour, breaking the previous 1-hour record set just 11 days earlier when Tropical Storm Henri soaked the region.

Rain in the desert

Less than 2 days earlier and a little over 3,000 miles to the southeast, Cyclone Shaheen made landfall in far northern Oman with winds just shy of a Category 1 hurricane.

The storm drenched the normally parched city of Al Khaburah with over 14 inches (300 mm) of rainfall in a matter of hours, according to The Times of Oman.

This is the equivalent of more than 3 years’ worth of rainfall in about 24 hours. In the nearby town of Suwaiq, more than a years’ worth of rain fell in just 6 hours. The storm produced a remarkable 4.57 inches (116 mm) of rainfall in a 6-hour span, exceeding what it typically sees in an entire year, according to Oman’s Meteorological Department.

A warming globe allows room for more rainfall

The significant increase in heavy rainstorms observed around the world is becoming more evident.

As the global temperatures rise, extreme precipitation events will drop more water, according to a report by the Intergovernmental Panel for Climate Change. The report highlighted that for every 1 degree Celsius (1.8°F) increase in air temperatures, the atmosphere can retain roughly 7% more water vapor.

In the US, the summer of 2021 exemplified this as tropical systems such as Ida and Henri rewrote the record books several times over in a span of weeks.

In August, Tennessee shattered its previous state record after 17 inches of rain fell in the town of McEwen in just 24 hours. A little over a week later, remnants of Hurricane Ida brought torrents of rainfall across the northeastern, setting daily and all-time records from New Jersey to New England.

These extreme rainfall rates are becoming more common because of human-caused global warming, scientists say. According to the UN’s report on climate change, “the frequency and intensity of heavy precipitation events have increased since the 1950s over most land area.”

Deadly flash floods also made headlines around the world this summer, including deadly floods in July across Western Europe, after several months’ worth of rain fell in hours, turning city streets in Belgium and Germany into torrents of water.

Heavy rainfall also caused floods in Central China in July that led to over 300 deaths. Zhengzhou, the provincial capital of 12 million people, was one of the hardest-hit areas, with entire neighborhoods submerged and passengers trapped in flooded subway cars.

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