ET, the storm was a Category One with sustained winds of 75 mph -- now it has sustained winds of 130 mph. While there isn't much definitive data on rapid intensification, a few key atmospheric ingredients help it occur, CNN meteorologist Michael Guy explained. Rapid intensification is rare: Because all those pieces must be in place, rapid intensification is rare, with just one or two Atlantic storms per year undergoing such an acceleration. That said, most storms that reach the highest categories, Cat 3, 4 and 5, reach these intensities through rapid intensification. Indeed, 70% of Atlantic storms that hit that mark do so through rapid intensification, according to a 2016 study published in Nature Communications.

Source: CNN September 10, 2018 14:08 UTC