In summary:
NOAA is forecasting a range of 12 to 17 total named storms (winds of 39 mph or higher). Of those, five to nine could become hurricanes (winds of 74 mph or higher), including one to four major hurricanes (Category 3, 4 or 5; with winds of 111 mph or higher). NOAA has a 70 percent confidence in these ranges.
While tropical storms can drop copious amounts of water that can cause significant flooding, it is the Category 3-4 storms that get the most attention. If you remember 2017, there were three large storms that hit the Gulf and southeast coasts of the USA — right in succession, bang, bang, bang! People who responded to that hurricane season will not forget 2017 for a long time.