Hurricane Irma was an extremely powerful and catastrophic cyclone, the strongest observed in the Atlantic Ocean since Wilma in 2005 in terms of maximum sustained winds. Irma developed on August 30, 2017 near the Cape Verde Islands, from a tropical wave that had moved off the west African coast three days prior. Under favorable conditions, Irma rapidly intensified shortly after formation.
The hurricane birth, spread and fade out has been filmed by Copernicus Sentinel-3A satellite with the SLSTR instrument. When the hurricane approached US coasts its strength began to fade out, its category was lowered and the wind speed was comparable to a tropical storm: indeed from this perspective one of the first clue observed in those images is the eye of the storm, no longer visible starting from September 9th.
Irma reached the top of its power on September 6th-8th, when the wind speed was around 300 km/h, its carried energy around 120 terajoules and the diameter of the eye of the storm 50 kilometers. The figures below picture a terrifying night view of the Hurricane at this stage of its development, approaching Central America and US coasts, captured by Sentinel-3A SLSTR instrument as well, then reprojected on Google Earth. Irma was classified as a category 5 Hurricane (sustaining wind speeds greater than 252 km/h), before reaching Cuba and Florida.
At the end of its journey the hurricane reached the Eastern coasts of the United States, when the US peninsula was completely enveloped by the storm at to the end of its race. One of the latest images of colossal Hurricane Irma wrapping Florida is showed below: this image has been acquired during the night of September 11th, around 22:00 P.M. local time in Miami.
Basically the wind speed is the most common metric for understanding the strength of a hurricane and Irma broke the record for several consecutive hours at Category 5 on September 7th. Anyway hurricane strength is about more than just maximum wind speed, for instance Energy is another important parameter because it can help to determine the storm’s impact, how bad it will be and how far it will extend. Thanks to its size and carried energy (112 terajoules) Irma can be considered one of the most devastating storms ever recorded in our Planet.
 “Tropical Storm Irma forms in Atlantic, and we’re still watching Gulf of Mexico early next week”. The Washington Post. ISSN 0190-8286
 “Hurricane Irma intensifies over the Atlantic”. CNBC. Reuters. September 1, 2017. Retrieved September 6, 2017.
 Koren (August 31, 2017). “Hurricane Irma Just Hit Category 3”. The Atlantic. Retrieved September 6, 2017.