The United States Agency for Ocean and Atmospheric Observation (Noaa ) predicted it… She confirms it. The 2020 hurricane season in the Atlantic is drawing to a close, with a record of thirty storms, thirteen of which mutated into hurricanes.
It exceeds 2005 and its twenty-eight storms, because it started early, on May 16, with Arthur, sweeping Bermuda. September 18, the storm Wilfred has exhausted the last of the twenty-one names reserved for the Atlantic. For the second time in meteorological history, the Greek alphabet had to be used for the end of the season, until Iota, ninth of the name, November 18.
What exactly is a storm?
A storm is officially named (under the aegis of the World Meteorological Organization, delegated to regional agencies) from the moment the winds exceed a speed of 63 km / h. It becomes a category 1 hurricane from 119 km / h. Then category 2 (154 to 177 km / h), even 3 (178 to 208 km / h) and 4 (209 to 251 km / h). Winds in category 5, the worst, exceed 251 km / h. Alone Iota, reached this level in 2020.
Are the consequences known?
The authorities of the countries concerned already deplore 409 deaths. Central America is just recovering from theAnd (169 deaths) and from Iota (61), the two hurricanes deadliest Atlantic of the year.
This is less than in 2005, marked by the terrible Katrina who blew up the dikes of New Orleans: 1,577 dead in Louisiana. But several hurricanes have triggered exceptional water levels and so has the property damage. The amounts of damage estimated by the communities or states affected in 2020 reach nearly 40,000 billion euros.
Why this record?
This is the fifth consecutive hurricane season above normal. And over the past twenty-six years, eighteen seasons also exceed the typical twelve storm average. This increased cyclonic activity is primarily attributed to a phenomenon called the “Atlantic multidecadal oscillation” (Amo, in English).
This variation in ocean surface temperatures has been in a positive phase since 1995, i.e. globally warm, explains specialist Thierry Huck, from the Physical and Spatial Oceanography Laboratory, in Brest. It is combined with other factors such as global warming of temperatures.
A warmer ocean generates more evaporation, and therefore more precipitation.
Europe, where the winter storm season started badly with Alex (at least nineteen dead) in October, is more sensitive to the Atlantic-North oscillation (Nao).
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