A hurricane hitting Miami is a well-known scenario for a disaster in the United States. It's also one that keeps many people up at night because there is nothing standing between Miami and a hurricane. As many others have said -- it is not if Miami will be devastated by a hurricane but when.
Over the past 48 hours, meteorologists have been bickering over projections of a storm forming in the Atlantic. Though it is too earlier to make definitive predictions about where the storm will go or how strong that storm will be many meteorologists are saying they would begin to take preparatory actions if they were in south Florida. The most current model shows a very real possibility of Miami being directly in the path (of course, these things can always turn and fizzle... fingers crossed). This is not even to mention the very real possibility of the storm crossing Florida and entering the Gulf of Mexico where it will find warm water to feed off of.
The Miami situation has been well documented in popular media. If you'd like to get caught up I recommend the following reading list