The history of Irma
Irma has gone down in the record books as the storm with the longest time spent as a Category 5 hurricane. This system has only been dominating headlines in the United States for the last couple of weeks, but Irma's been around for much longer.
Irma first formed into a tropical storm with 50 mph winds over the far eastern Atlantic on August 30th, 2017. The storm then intensified and become a hurricane on Friday, September 1st. Over the next 11 days, Irma would continue to grow into a major hurricane before making landfall over the northern Leeward Islands on Wednesday, September 6th. This system did weaken some, back to a Category 3 storm, as it interacted with Cuba after making its 3rd landfall. However, once Irma made that turn towards the north, it re-intensified again, thanks to the warmer waters of the Florida Straits. Finally, after making landfall over the Florida Keys and Marco Island, the system lost its hurricane status and became a tropical storm earlier yesterday. It is now a tropical depression this morning.
Atmospheric conditions were just right over the last 2 weeks, allowing Irma to gain Category 5 strength at times. The Atlantic waters are at their warmest during this time of the year, supplying the energy hurricanes need to thrive. Also, this hurricane continued to hold together throughout its life thanks to the lack of wind shear over the ocean. Lastly, high pressure located directly above the storm served a "breathing" mechanism for Irma, allowing rising air to travel through the eye and out away from the storm.